Hamuli in the Hymenoptera (Insecta) and their phylogenetic implications

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Hamuli in the Hymenoptera (Insecta) and their phylogenetic implicationsH. H. Basibuyukabc; D. L. J. Quickeab

a Department of Biology, Imperial College, Ascot, UK b Department of Entomology, Natural HistoryMuseum, London, UK c Department of Biology, Cumhuriyet University, Sivas, Turkey

To cite this Article Basibuyuk, H. H. and Quicke, D. L. J.(1997) 'Hamuli in the Hymenoptera (Insecta) and theirphylogenetic implications', Journal of Natural History, 31: 10, 1563 — 1585To link to this Article: DOI: 10.1080/00222939700770831URL: http://dx.doi.org/10.1080/00222939700770831

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JOURNAL OF NATURAL HISTORY, 1997, 31, 1563 1585

Hamuli in the Hymenoptera (Insecta) and their phylogenetic implications

H. H. B A S I B U Y U K t * and D. L. J. QUICKE+ +

4fDepartment of Biology, Imperial College, Silwood Park, Ascot, Berkshire, SL5 7P Y, UK; Department of Entomology, Natural History Museum, London, SW7 5BD, UK; and Department of Biology, Cumhuriyet University, 58140-Sivas, Turkey ~Department of Biology, Imperial College, Silwood Park, Ascot, Berkshire, SL5 7P II, UK and Department of Entomology, Natural History Museum, London, SW7 5BD, UK

(Accepted 7 February 1997)

Hamuli are hook-like setae on the anterior margin of the hind wing which interlock with the recurved posterior edge of the fore wing in the Hymenoptera during flight, making them functionally two winged. The possession of hamuli is an autapomorphy for the Hymenoptera. Three types of hamuli are distinguish- able: basal hamuli, distal hamuli and secondary hamuli. Basal hamuli occur only in the Xyelidae, Pamphiliidae and Xiphydriidae. Secondary hamuli occur in two common forms in terms of their arrangement: openly spaced (dispersed) or clustered. Dispersed secondary hamuli are hypothesised as plesiomorphic and clustering is a putative synapomorphy for several groups within the order. Distal hamuli are present in all winged Hymenoptera. The presence of a modified and erect setal band opposing distal hamuli may be a synapomorphy for Chalcidoidea + Ceraphronoidea + Diapriidae + a new family to be described from New Zealand.

KEYWORDS; Hymenoptera, hamuli, morphology, phylogeny.

Introduction Current ideas on the evolution of the Hymenoptera mostly rely on Rasnitsyn

(1988) which is the first fully resolved phylogenetic hypothesis of family level relationships within the order. However, it was not based on a formal computerised analysis and it cannot be considered to be the most parsimonious solution. Moreover, Rasnitsyn's phylogeny was restricted by the data available at that time. Recent studies have dealt with the aculeate Hymenoptera in more detail, and take into account more data. This has resulted in a well supported phylogenetic hypothesis for that clade (Brothers, 1975; Carpenter 1986; Brothers and Carpenter, 1993). However, few solid conclusions can be drawn concerning the higher level phylogeny

*To whom correspondence should be addressed.

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1564 H.H. Basibuyuk and D. L. J. Quicke

of the rest of the order, though in recent years, a growing body of evidence suggests that the Xyelidae are the most ancient extant family of the Hymenoptera (Gibson, 1993), the Orussidae and Apocrita are sister groups (Gibson, 1985; Johnson 1988; Whitfield et al., 1989; Basibuyuk and Quicke, 1995; Vilhelmsen, 1996), and the Ichneumonoidea and Aculeata are closely related (Zessin, 1985; Quicke et aL, 1992a; Sharkey and Wahl, 1992; Basibuyuk and Quicke, 1995).

Although, the number of morphological studies providing potential phylogenetic information has increased greatly over the past few years (Gibson, 1985, 1986; Darling, 1988; Johnson, 1988; Whitfield et al., 1989; Quicke et al., 1992a,b, 1994; Heraty et al., 1994; Basibuyuk and Quicke, 1995; Vilhelmsen, 1996) an enormous number of potentially promising morphological character systems still remain to be studied. The most reliable and informative phylogenetic estimates can be expected to result from analysis of the largest and most complete data set possible. In this paper we draw attention to the potential phylogenetic significance of variation in a familiar, but hitherto little studied, character system in the Hymenoptera, the hamuli.

Hamuli are seta-like structures, and each presumably arises from a single modified epidermal cell (Richards and Davis, 1977). Possession of hamuli, hooked setae, on the anterior margin of hind wing is recognised as an unique diagnostic character for adult winged hymenopterans (Gauld and Bolton, 1988; Mason and Huber, 1993; Hanson and Gauld, 1995; Quicke, 1997). With the exception of general notes in entomological textbooks, there have, however, been only a few studies on these structures which serve to couple the fore and hind wings during flight (Fig. 1A). Those studies that have been conducted, have covered only a limited part of the order and have not made use of high resolution techniques (e.g. Quicke, 1981 ), Here we have employed electron microscopy to obtain more information on the different types of hamuli found throughout the Hymenoptera and their possible phylogenetic significance.

Material and methods Both dry pinned specimens and ethanol preserved material were employed. Most

were prepared for standard scanning electron microscopy as follows: hind wings were removed and transferred to dry ethanol for at least 18 h, cleaned using an ultrasonic cleaner, then air dried and mounted on a microscope stub prior to sputter coating with gold. Specimens were examined using either a Cambridge 150 Mark II or Hitachi $800 microscope. Some light microscopy slides were also prepared as follows: hind wings were removed and transferred to dry ethanol for at least 24 h, then transferred to Histoclear (National Diagnostics) for 1 h, cleaned using an ultrasonic cleaner, then mounted between slide and cover slip in a drop of His tomoun t (National Diagnostics). Some material in the slide collection of the Natural History Museum, London, was also studied. Material examined is listed in Appendix 1. The terminology for wing venation and folds follows Richards (1977). Family arrangement follows Gauld and Bolton (1988), except that Platygastroidea are recognised in accordance with Goulet and Huber (1993), families of Cynipoidea follow Ronquist (1995a), and the Eumenidae is regarded as a subfamily of Vespidae (Carpenter, 1982).

Results Hamuli sit in a well-developed socket with their base attached by an articulating

ring of membrane (Fig. 1B). Three classes can be distinguished on the basis of


Hamuli in the Hymenoptera 1565

Fro. 1. Wing coupling and hamuli: (A) wing coupling in Vespula consobrina (Vespidae). Scale: 215/~m; (B) distal hamuli in a socket (Diodontus sp.: Sphecidae). Scale: 15#m. (C) Basal hamuli (MacroxyelaJerruginea: Xyelidae). Scale: 50 #m.

position on the wing margin and their structure, but previous terminology has been confusing. The term 'basal hamuli' has often been used for both 'true' basal hamuli (recognised by Rasnitsyn, 1969) and secondary hamuli (or hooked macrotrichia) (recognised by Riek, 1970) and, in particular, for clustered secondary hamuli that are usually situated basally on the costal vein. However, these two distinct types of



basal hamuli appear not to be homologous for two reasons: (i) their structure, size and placement are different (see below); and (ii) both types occur together in species of Xyelidae, Pamphiliidae and some Xiphidriidae, showing that they are distinct entities. To avoid confusion and misinterpretation, we term the three types of hamuli: basal hamuli (Fig. 1C), secondary hamuli (Fig. 2A, B), and distal hamuli (Fig. 2C). The distribution of, and variation in, each of these is detailed below and the results are summarised in Table 1.

Basal hamuli Basal hamuli comprise a closely-spaced set of modified hooks that are clustered

on the very basal part of the costal vein, at the separation of costa and subcosta (Fig. 2D). They curve over towards the wing apex and are twisted approximately one third of the distance from their base and are apically flattened and sometimes longitudinally striate in members of all three families (Fig. 1C). They are never bifurcate or furnished with a preapical spur. Basal hamuli are only possessed by the members of three symphytan families, the Xyelidae, Pamphiliidae and Xiphydriidae, but within these they were present in all species examined. Although the number of basal hamuli are variable within and among these three families (Table 2), their structure is similar in all species examined.

Secondary hamuli Secondary hamuli are not hook-like structures as in the case of basal and distal

hamuli. They may be slightly bent, and often have the tip bifurcated with a small hook (Fig. 2A, B). Secondary hamuli can be divided into two subgroups: (i) dispersed, in which they are widely spaced along the costal vein proximal to the distal hamuli (Figs. 2D, 3A); and (ii) clustered, in which they are restricted to a limited length (area) and form a tight group on the costal vein, usually beyond the separation of the costa and subcosta+radius (Figs. 2D, 3B). Within the Symphyta more or less well-developed secondary hamuli are present in most members of the families Xyelidae, Pamphiliidae, Blasticotomidae, Anaxyelidae, Cephidae and Orussidae, and also in many members of the Argidae, Pergidae, Tenthredinidae, Siricidae and Xiphydriidae (Fig. 4A), and they are almost always dispersed although they tend to form a cluster basally in members of the argid, Zenarge turneri. They are also present in nearly all aculeates including all members of the Chrysidoidea and Apoidea, and most Vepoidea (original observations and Brothers and Carpenter, 1993, the latter referring to them as basal hamuli).

Clustered secondary hamuli, which almost always form a basal group, are found in two superfamilies of the parasitic Apocrita, the Trigonalyoidea and Ichneumonoidea (Figs. 2A, 3B, 4B). In the Braconidae, however, the secondary hamuli are less developed, and usually take the form of erect setae (Quicke, 1981) rather than being hooked as in the ichneumonidae. Some members of the vespoid families, the Mutillidae, Bradynobaenidae, Rhopalosomatidae, and Pompilidae also have clustered secondary hamuli. These hamuli are well-developed and in the Rhopalosomatidae have a bifurcate apex (Fig. 2B). Some megalyrids are unique among hymenopterans in that the clustered secondary hamuli form a distal rather than a basal group, these being situated immediately before the distal hamuli (Fig. 4C). Members of four megalyrid genera were studied. Only Megalyra species display this form of secondary hamuli; Carminator, Ettchellsia and Dinapsis lack secondary hamuli (Table 3).



• > . . . . .

dsh i ,

dh

. . . . ~ i ii:i~ '~

kdh

• • , < : " :,,,'!:,:," •

FIG. 2. Secondary (A,B) and distal (C) hamuli with their positions illustrated (D): (A) Trigonalis hahnii (Trigonalyidae). Scale: 50/~m; (B) Rhopalosoma sp. (Rhopalosomatidae). Scale: 40~lm; (C) Bembix sp. (Sphecidae). Scale: 215#m; (D), Schematic view of hamuli position on hind wings of the Symphyta (upper), and Apocrita (lower): (bh) basal hamuli, (dh) distal hamuli, (dsh) dispersed secondary hamuli, (sh) secondary hamuli.


1568 H . H . B a s i b u y u k a n d D. L. J. Q u i c k e

Table 1. Summary of some selected features of hamuli in the Hymenoptera .

Characters Characters

Taxa A B C D E F Taxa A B C D E F

Xyelidae 0 0 0 0 0 0 Platygastroidea 1 1 - - 1 0 1 Pamphil i idae 0 p 0 p 0 0 Chalcidoidea 1 1 - - 1 1 1 Megalodont idae 1 1 - - 1 0 0 Mymar idae 1 1 - - 1 ? 1 Blasticotomidae 1 0 0 0 0 0 Ichneumonidae 1 0 1 1 0 p Pergidae 1 1 - - 1 0 0 Braconidae 1 0 1 1 0 p Argidae 1 p 1 p 0 0 Bethylidae 1 0 0 1 0 1 Cimbicidae 1 1 - - 0 0 0 Chrysididae 1 0 0 1 0 0 Tenthredinidae 1 p 0 0 0 0 Dryinidae 1 0 0 1 0 1 Dipr ionidae 1 0 0 0 0 0 Embolemidae? 1 0 0 1 0 ? Cephidae 1 0 0 1 0 0 Plumariidae 1 0 0 1 0 1 Anaxyel idae 1 0 0 1 0 0 Sclerogibbidae 1 0 0 1 0 1 Siricidae 1 p 0 0 0 0 Scolebythidae 1 0 0 1 0 1 Xiphydri idae 0 1 - - 1 0 0 Bradynobaenidae 1 p 1 1 0 0 Orussidae 1 0 0 1 0 p Formicidae? 1 1 - - 1 0 ? Trigonalyidae 1 0 1 1 0 0 some formicids$ 1 0 0 1 0 0 Megalyridae 1 p 2 1 0 p Mutillidae'~ t O 1 i 0 ? Stephanidae 1 1 - - 1 0 1 Pompil idae 1 0 1 1 0 0 Evaniidae 1 1 - - 1 0 0 Rhopalosomat idae 1 0 1 1 0 0 Aulacidae 1 1 - - 1 0 1 Sapygidae 1 0 0 1 0 0 Gasterupt i idae 1 1 - - 1 0 1 Scoliidae 1 1 - - 1 0 0 Cynipoidea 1 1 - - 1 0 1 Sierolomorphidae t 1 0 0 1 0 ? Ceraphronoidea 1 1 - - 1 1 1 Tiphiidae~ 1 0 0 1 0 0 Pelecinidae 1 1 - - 1 0 0 Vespidae 1 1 - - 1 0 0 Diapri idae 1 1 - - 1 1 1 Apidae 1 0 0 1 0 0 other proctotrupoids 1 1 - - l 0 1 Sphecidae 1 0 0 1 0 0

(?) missing data, (@ inapplicable, (p) polymorphic. tBrothers and Carpenter (1993); :~Baroni Urbani et al. (1992). A. Basal hamuli: 0 = present; 1 = absent. B. Secondary hamuli: 0 = present; 1 = absent. C. Secondary hamuli (if present): 0 = dispersed (widely spaced); 1 = forming a basal cluster

2 = forming an apical cluster. D. Distal hamuli placement: 0=z igzag line; 1 =s t ra ight line. E. Addit ional erect setae opposite to distal hamuli: 0 = absent; 1 = present. F. Distal hamuli comprising: 0 = m o r e than four hooks; 1 = f o u r or fewer hooks.

Distal hamuli D i s t a l h a m u l i a re p r e sen t in all a l a t e H y m e n o p t e r a . T h e y are l o c a t e d a t the

a n t e r i o r m a r g i n o f the h i n d wing b e y o n d its m i d - p o i n t , u sua l l y where the first r a d i a l ve in occu r s (F ig . 2C, D) . D i s t a l h a m u l i a re u sua l l y m o r e o r less S - s h a p e d , a n d the i r ap ices a re t yp i ca l ly f o r m e d in to h o o k s t h a t a re r e s p o n s i b l e fo r i n t e r l o c k i n g wi th the sc le ro t i sed fo ld ( f rena l f o l d ) o f the p o s t e r i o r edge o f fore w ing d u r i n g f l ight (F ig . 5A) . Th i s c o u p l i n g un i t e s the fo re a n d h i n d wings in to a s ingle a i r fo i l ( F i g . 1A).

D i s t a l h a m u l i f o r m a s ingle s t r a i g h t l ine in m o s t fami l ies o f H y m e n o p t e r a (F ig . 5B) b u t in m a n y m e m b e r s o f s o m e s y m p h y t a n famil ies , viz. the X y e l i d a e ( F i g . 6 A ) , Acantholyda ( P a m p h i l i i d a e ) , T e n t h r e d i n o i d e a (except pe rg ids a n d s o m e a rg ids ) (F ig s . 5C, 6B), a n d S i r ic idae , t hey are e i ther c o m p l e t e l y o r p a r t l y a r r a n g e d in a z igzag l ine g iv ing the i m p r e s s i o n o f two or th ree rows ( T a b l e 2) .

T h e n u m b e r o f d i s ta l h a m u l i va r i e s wide ly w i th in the O r d e r r a n g i n g f r o m two


Hamuli in the Hymenoptera

Table 2. Some selected hamuli features in non-aculeate families.

1569

Basal hamuli Secondary Distal hamuli Distal hamuli Taxa number hamuli number number orientation

Xyelidae 12-13 5 15 15 25 zigzag Pamphiliidae 7-9 3 5 12 13 polymorphic Megalodontidae absent absent 8 17 linear Argidae absent absent or 5 6 7 ll polymorphic Blasticotomidae absent 4 6 5 6 zigzag Cimbicidae absent absent 18 27 zigzag Diprionidae absent absent 8-12 zigzag Pergidae absent 3 5 5 11 linear Tenthredinidae absent 3-6 8-14 zigzag Cephidae absent 6 11 6-10 linear Anaxyelidae absent 7-8 8 linear Siricidae absent 3 5 30 60 zigzag Xiphydriidae 4-13 absent 6 19 linear Orussidae absent absent or 1-6 4-6 linear Trigonalyidae absent 1 17 7 14 linear Evaniidae absent absent 7-10 linear Aulacidae absent absent 2-3 linear Gasteruptiidae absent absent 3 linear Megalyridae absent 1 7 2 6 linear Stephanidae absent absent 3 4 linear Cynipoidea absent absent 2 4 linear Ceraphronoidea absent absent 2 3 linear Proctotrupoidea absent absent 2-3 linear Pelecinidae absent absent 6 7 linear Platygastroidea absent absent 2 3 linear Chalcidoidea absent absent 2-4 linear Ichneumonoidea absent absent or 1-many 3-30 or more linear

(Leptacis sp., Platygastridae) to sixty (Urocerus gigas, Siricidae) or more (some sphecid wasps). However, the variation within some superfamilies is often far more constrained, and may be fixed. In the Aulacidae, Gasteruptiidae (Fig. 7A), Stephanoidea (Fig. 7B), Cynipoidea (Fig. 8A), Chalcidoidea including Mymaridae (Fig. 8B, C) (with exception of some Conura spp., Delvare and Boucek, 1992), Ceraphronoidea (Fig. 8D), Proctotrupoidea (except Pelecinidae) and Platygastroidea, there are always fewer than five. In the Megalyroidea and Ichneumonoidea, distal hamuli number ranges from 2-6 and 3 30 respectively. Many megalyrids have two or three distal hamuli but both sexes of Megalyra fasciipennis and Ettchellsia pilliceps and some female individuals of M. rufipes, and M. shuckardi have more than four distal hamuli (Table 3).

The most basal, or sometimes the most basal pair of distal hamuli are generally straight or less modified than the remainder in the Cynipoidea, Ceraphronoidea, Chalcidoidea (Fig. 8A-D). In the Cynipoidea, Ceraphronoidea, Platygastroidea, Mymaridae, many Chalcidoidea and Proctotrupoidea, the distal hamuli are located on a well-pronounced projection (Figs. 8A-D). In some of these (Chalcidoidea, Mymaridae, Diapriidae and Ceraphronoidea) there is a distinct group of modified- erect seta, usually forming an orderly row, which opposes the distal hamuli (Fig. 8B-D, Table 1). Members of the new family to be described from New Zealand by J. Early, L. Masner and I. Naumann also have the hamuli on a projection and


1570 H . H . Basibuyuk and D. L. J. Quicke

FIG. 3. Secondary hamuli: (A) dispersed (Trachelus tabidus: Cephidae). Scale: 10/~m; (B) clustered; arrows (Orthogonalys pulchella: Trigonalyidae). Scale: 100#m.

have a row of erect setae. However, the row of erect setae is absent from other Proctotrupoidea (including Pelecinidae), Cynipoidea, Evanioidea s.1., Megalyroidea, Stephanoidea, Trigonalyoidea and the Ichneumonoidea + Aculeata clade.



F~G. 4. Secondary hamuli: (A) dispersed secondary hamuli (Urocerus gigas: Siricidae). Scale: 7"5 pro; (B) basal cluster (Ophion sp. : Ichneumonoidea). Scale: 125 #m; (C) distal cluster; arrows (Megalyrafasciipennis: Megalyridae). Scale: 50 gin.

Discussion The hamulate type wing coupling mechanism is an autapomorphy of the

Hymenoptera (Gauld and Bolton, 1988; Naumann, 1991; Mason and Huber, 1993; Hanson and Gauld, 1995) (Fig. 1A). Nevertheless, variation in the structure,



Table 3. Hamuli number of some species of the Megalyridae. (F) female; (M) male.

Taxa Secondary hamuli number Distal hamuli number

Carminator sp. absent 3 C. ater absent 3 4 Dinapsis turneri absent 3 Ettchellsia piliceps absent 5 Megalyrafasciipennis 5 (M), 6-7 (F) 5 (M), 5-6 (F) M. longiseta 1 (M), 3 (F) 2 (M), 3 (F) M. rufipes 2 (F) or 6 (F) 3-5 (F) M. rufiventris 3 (M/F) 3 (M/F) M. shuckardi 2 (M), 6 (F) 2 (M), 5 (F) M. testaceipes 1 (M/F) 2 (M/F) M. wagneri 2 (F) 2 (F)

location and numbers of hamuli and some related structures appears to provide additional information concerning phylogenetic relationships within the order. Basal and secondary hamuli may also be involved in wing coupling but at least in the Braconidae, the simple setiform secondary hamuli probably serve to provide support for the posterobasal part of the forewing only during the upstroke rather than interlocking the wings on both strokes (Quicke, 1981).

Because homologous hamuli are not present in any other insect group, it is not possible to use outgroups among other insect orders to polarize the various character states. Determination of the groundplan structure for the wing coupling apparatus in the Hymenoptera has therefore to be based on relationships and character state distributions within the Hymenoptera. The Xyelidae display many plesiomorphic features (Rasnitsyn, 1969, 1980; Gibson, 1993) and the oldest known fossil Hymenoptera belong to the Xyelidae (Rasnitsyn, 1980). Furthermore, recent character surveys provide convincing evidence that the Xyelidae form the sister group to the remaining extant Hymenoptera (Gibson, 1993; Heraty et al., 1994) (Fig. 9). Here we accept this evidence and use the xyelids as an outgroup to polarise character states in the remaining Hymenoptera.

Phylogenetic implications - - basal hamuli Basal hamuli are present in the Xyelidae (Xyelini and Macroxyelini),

Pamphiliidae and Xiphydriidae. Rasnitsyn (1969) clearly stated that the Xyelidae and Pamphiliidae possess both basal and distal hamuli but he also added that they are present in the Xiphydriidae and some Siricidae. However, we did not observe basal hamuli in any extant siricid wasp. Day (1988) did not differentiate between basal and clustered secondary hamuli and commented that the clustered secondary hamuli in the Rhopalosomatidae are more similar to the basal hamuli of Xyelidae than they are to those of the Pompilidae. It has been reported that some ant genera have 'basal hamuli', both sexes of some Myrmecia and Amblyopone species and males of Nothomyrmecia (Baroni Urbani et al., 1992). However, our observations confirm that these are dispersed secondary hamuli rather than basal ones. The most parsimonious interpretation of the distribution of basal hamuli given current hypo- theses for hymenopteran phylogeny (Rasnitsyn, 1988; Heraty et al., 1994) is three independent acquisitions in these families which requires only three steps (see Fig. 9).



FIG. 5. (A) Sclerotised posterior margin of fore wing (frenal fold) in Perga dorsal& (Pergidae). Scale: 10 #m; (B) flattened and evenly spaced distal hamuli in Orussus sp. (Orussidae). Scale: 50/~m; (C) zig zag orientation of distal hamuli in Blasticotoma filiceti (Blasticotomidae). Scale: 75 #m.

If basal hamuli are instead taken to be part of the hymenopteran groundplan (because they are present in xyelids), then at least three steps (gains and losses) are required in the non-xyeline Hymenoptera, but this ignores the necessary gain that



FIG. 6. Zigzag orientated distal hamuli: (A) Macroxyelaferruginea (Xyelidae). Scale: 10 #m; (B) Nematus tibialis (Tenthredinidae). Scale: 20#m.

has to be postulated for the common ancestor of the Xyelidae and non-xyelid Hymenoptera, which makes a total of four steps. Determination of whether basal hamuli are part of the hymenopteran groundplan or not may be possible with more



FIG. 7. Distal hamuli: (A) Gasteruption sp. (Gasteruptiidae), note distinctly spaced first hook (arrow). Scale: 50/~m; (B) Parastephanellus sp. (Stephanidae), note less well-developed first hook (arrow). Scale: 10/~m.



FIG. 8. Projected anterior edge of hind wing with distal hamuli (note less well-developed first hook), and with a set of erect setae (arrows): (A) Liopteron sp. (Liopteridae). Scale: 22#m; (B) Sympiesis sp. (Eulophidae). Scale: 10 #m; (C) gen. sp. (Mymaridae). Scale: 3'7/tm; (D) Dendrocerus carpenteri (Megaspilidae). Scale: 10 #m.

FIG. 9. Phylogenetic hypothesis for Hymenoptera based on Rasnitsyn (1988) but with modi- fications according to Heraty et al. (1994), and Brothers and Carpenter (1993) [Note this does not claim a biphyletic origin for the non-xyelid Hymenoptera whereas Rasnitsyn (1988) does].



Xyelidae Pamphiliidae Megalodontidae Argidae Pergidae

[

J

~ Cimbicidae Blastocotomidae Cephidae Anaxyelidae Siricidae Xiphydriidae Orussidae

~ Stephanidae Megalyridae Trigonalyidae Ceraphronidae Megaspilidae Aulacidae

r---k._ Gasteruptiidae I Evaniidae

~ Cynipoidea Diapriidae Monomachidae Austroniidae Peradiniidae Heloridae Roproniidae Proctotrupidae Vanhomiidae

I | Pelecinidae ] ~ Scelionidae I [---1-

I ~ Chaiddoidea L--- Mymaridae r - Braconidae

Ichneumonidae ~ . . _ ~ Bethylidae

Chrysididae Embolemidae Dryinidae

~ Scolebythidae I I Sclerogibbidae

~ Plunmriidae Tiphiidae Pompilidae Mutillidae Sapygidae Rhopalosomatidae Vespidae Scoliidae Formiddae a ~ b a e n i d a e Sierolomorphidae Sphecidae

L _ Apidae



detailed study of fossil sawflies, but their distribution among extant taxa is apparently phylogenetically uninformative at family level.

Phylogenetic implications - - secondary hamuli Secondary hamuli are patchily distributed among the sawflies, and are not

consistently present in all members of several families (i.e. Argidae and Xiphydriidae), making discussion of their evolution in that basal grade difficult (Table 2). Their occurrence may, however, be more phylogenetically informative among the Apocrita. Given that secondary hamuli are present in at least some members of the Anaxyelidae, Siricidae, Xiphydriidae and Orussidae, i.e. the grade leading to the Apocrita (Fig. 9), it seems highly probable that they were present in the ancestor of the Apocrita. Given the phylogeny presented in Fig. 9, their presence in megalyrids and trigonalyids requires either one gain and two losses or two gains and one loss in that part of the tree. Their absence in the Chalcidoidea+ Mymaridae + Proctotrupoidea + Cynipoidea + Platygastroidea may be considered as a synapomorphy for that large clade. However, the alternative hypothesis, that secondary hamuli were absent from the ancester of the Apocrita would be equally parsimonious.

Within the aculeate Hymenoptera secondary hamuli are present in all taxa except brachycistidine tiphiids, bradynobaenine and apterogynine bradynobaenids, Scoliidae, and Vespidae (Brothers and Carpenter, 1993). These authors also reported them to be absent from Formicidae, however, Baroni Urbani et al. (1992) reported what are dispersed secondary hamuli in some ants genera so they are actually polymorphic in that family. This distribution suggests that secondary hamuli were present in the ancestral aculeates and have been subsequently lost in these few groups. Absence in vespids and scoliids may be synapomorphic for that clade.

Most families and superfamilies possess only one of the two types of secondary hamuli, clustered or dispersed, the only exception being the Argidae in one genus of which (Zenarge), dispersed secondary hamuli tend to form a basal cluster whereas the other had dispersed ones. Within the Aculeata, clustered secondary hamuli are only found in the Vespoidea and then not in all families, viz. the Mutillidae, Bradynobaenidae, Rhopalosomatidae and Pompilidae (Day, 1988; Brothers and Carpenter, 1993). The universality of dispersed secondary hamuli in the Chrysidoidea and Apoidea strongly suggests that this is also the ancestral state for the Vespoidea. In this case, several independent acquisitions of clustered hamuli have to be postulated in that superfamily. Clustered secondary hamuli are also a prominent feature of the Trigonalyidae and Ichneumonoidea, though, in the Braconidae these hamuli, although well-developed, are not hooked at the apex (Riek, 1970; Quicke, 1981). Given that all sawflies with secondary hamuli have dispersed ones, it is also most likely that clustering evolved independently in these, minimally on two occasions.

Phylogenetic implications distal hamuli Arrangement of distal hamuli in a zigzag line occurs in members of many

symphytan families, i.e. Xyelidae, Pamphiliidae (Acantholyda), Tenthredinoidea (except pergids and some argids) and Siricidae (Fig. 6A, B), may be considered the plesiomorphic condition for the Hymenoptera (Rasnitsyn, 1988; Gibson, 1993; Heraty et al., 1994). As with basal hamuli, interpreting the evolutionary changes that have taken place depends on whether the state displayed by the Xyelidae is considered as the groundplan for the Order. If the xyelid condition is taken as the



groundplan then a minimum of six evolutionary steps are required (including the polymorphism within the Pamphiliidae and Tenthredinoidea but excluding acquisi- tion at the base of the Hymenoptera, the plesiomorphic state), and the same number is required for independent acquisitions in the xyelid, pamphiliid, tenthredinoid and siricid lineages. At superfamily level this character seems to provide little phylogenetic information, however, it might be more useful within the Pamphiliidae and the Tenthredinoidea.

The number of distal hamuli varies considerably within the order, but is virtually constant in the Stephanoidea, Cynipoidea, Ceraphronoidea, Proctotrupoidea, Platygastroidea and Chalcidoidea (ie. 'microhymenoptera' s e n s u Mason, 1983 unpublished) and also in some basal apocritan families, in nearly all of which there are three (rarely two or four) hamuli (Tables 2, 4). In some cases, internal phylogenies of the families or superfamilies allow postulation of the groundplan number. For example, although distal hamuli number varies from two to four in the Cynipoidea, the phylogeny reconstructed for the basal families in that group shows clearly that

Table 4. Hamuli numbers and body length in some selected taxa of Hymenoptera.

Taxa Distal hamuli number Body length (mm)'~

Xyelidae 15-25 5-15 Pamphiliidae 12-13 7-15 Argidae 7-11 4-12 Blasticotomidae 5-6 7-9 Cimbicidae 18-27 9-28 Diprionidae 8-12 5 10 Pergidae 5-11 3-15 Tenthredinidae 8-14 2.5-15 Cephidae 6-10 4 18 Siricidae 30-60 10-55 Xiphydriidae 6-19 4-25 Orussidae 4-6 2.2 15 Trigonalyidae 7- ! 4 5 13 Evaniidae 7-10 1"7 17 Aulacidae 2-3 4-45 Gasteruptiidae 3 3.3 85 Megalyridae 2-6 2-5 100 Stephanidae 2-4 3.5 60 Ibaliidae 2-3 4 30 Liopteridae:~ 3 1.4 15 other Cynipoidea 3-4 1-6 Ceraphronoidea 2-3 0.5 4 Austroniidae 2-3 4-6 Diapriidae 3 1 8 Heloridae 3 4 5 Monomachidae 2-4 6 18 Proctotrupidae 3 3 15 Pelecinidae 6-7 20-70 Platygastroidea 2-3 0-5 10 Chalcidoidea 2-4 0.2-20 (mostly <2) Ichneumonidae 3-30 2-61 or more (120) Braconidae 3-8 1 14

t Body length is mostly extracted from Gauld and Bolton (1988), Naumann (1991) and Hanson and Gauld (1995); :~Ronquist (1995b).



the ancestral state was possession of three distal hamuli (Ronquist, 1995a; Nordlander et al., 1996). The range of distal hamuli number is 3-30 within Ichneumonoidea however the common number appears to be about ten in the Ichneumonidae (Townes, 1969). Given the phylogeny proposed by Sharkey and Wahl (1992), five or more is likely to be groundplan condition for the Ichneumonoidea. Within the Megalyridae the distal hamuli number also varies from two to six (Table 3). Megalyra appears from Shaw's (1990) phylogenetic analysis of the Megalyridae to be the most basal genus examined here. Unfortunately, it displays the whole range of variation in hamuli number found in the family making it difficult to determine the groundplan number for the family.

It has often been claimed that there is a correlation between the number of hamuli and size of the insect (Riek, 1970; Quicke, 1981). Our findings for the Pelecinidae, a family of relatively large proctotrupoids, in which the number ranges from six to seven rather than two to three, tend to support this, though size per se may not be the only factor as, for example, there is some evidence that hamuli number is related with the flight range rather than size in foraging bees (Abrol, 1986). Size-dependency in a character may pose considerable problems for its use in phylogenetic analysis, because of the very obvious possibility of homoplasy. A reduced number and virtual fixation at three in many cases may be a synapomorphy for two reasons. Firstly, more than four hamuli are present in all symphytan taxa except for the Orussidae which have comparatively fewer (Tables 2, 4). Secondly, the correlation between small size and decrease of distal hamuli number cannot be applied to all taxa; members of the Aulacidae, Gasteruptiidae and Stephanidae, and many members of megalyrid, ichneumonoid and aculeate wasps which are much larger in size have few distal hamuli (four or fewer) while small species in some other families (e.g. Evaniidae, Trigonalyidae) can have considerably more than four (Table 4). Detailed interpretation is difficult and it could be argued either that reduction to three is a synapomorphy for the 'microhymenoptera' (see above) with the Pelecinidae providing a size-related reversal, or that a reduced number was a basal feature of the Apocrita and that several reversals including in the evaniids, trigonalyids and various ichneumonoids and aculeates.

Perhaps the most phylogenetically informative character revealed by the present study is the presence of a row of modified-erect setae opposing the distal hamuli in some families (Fig. 8B-D). This provides a putative synapomorphy for a clade comprising the Chalcidoidea, Ceraphronoidea, Mymaridae, Diapriidae and a new family from New Zealand to be described by J. Early, L. Masner and I. Naumann. The placement of the Ceraphronoidea within the Evaniomorpha as proposed by Rasnitsyn (1980, 1988) is, therefore, not supported by this feature. It should be noted however, that most of the species in these taxa are small, and therefore the possibility that it could be a size-related convergence cannot be excluded at this time.

Acknowledgements We would like to thank Mr Suphan Karaytug (NHM/London) for line drawings.

Thanks to The Natural History Museum (London) for providing facilities; to the staff of the Photographic Unit for producing excellent SEM micrographs; Dave Smith (Washington) for loan of a specimen of Megaxyela; and Alexandr Rasnitsyn (Moscow), Fredrik Ronquist (Uppsala) and an anonymous referee for their very valuable comments.



Appendix List of material examined

Most of the specimens were examined by SEM (scanning electron microscopy), taxa observed only from light microscope slides are indicated by (LMS). When both SEM and LMS observations were made for the same specimen, this is indicated by *. Additional binocular light microscopic observation of intact specimens is indicated by (BLM). Male and female specimens are indicated by M and F respectively. Xyeloidea. Xyelidae: Macroxyela ferruginea (Say), F, N America; Macroxyela sp., F, USA; Megaxyela bicoloripes (Rohwer), F, USA (BLM); Xyelajulii (Br6bisson), F, UK. Megalodontoidea. Pamphilidae: Acantholyda erythrocephala (L.), F, Canada; A. serbica Vasic, F, Yugoslavia (BLM); A. pumilionis Giraud, F, Switzerland (BLM); Pamphilius stramineipes (Hartig), F, C.S.S.R.; P. sylvaticus (L.), F, UK Megalodonitidae: Megalodontes klugi Leach, F,? (LMS); *Megalodontes turcicus Mocsary, F, Turkey. Tenthredinoidea. Argidae: *Arge cyanocrocea (F6rster), F, France; Digelasinus diversipes Kirby, F, Brasil (BLM); Pachylota audouinii Westwood, F, Brasil (BLM); Pampsilota afer Konow, F, Africa (BLM); Sterictiphora geminata L., F, UK (BLM); Zenarge turneri. Rohwer, M, Australia (BLM). Blasticotomidae: Blasticotomafiliceti Malaise, F, Japan. Cimbicidae: Abia candens Konow, F, UK; Abia sericea (L.), F, UK (LMS); *Cimbex sp., F, UK. Diprionidae: *Diprionpini (L.), F, UK. Pergidae: Antiperga antiopa Morice, F, W Australia (BLM); *Lophyrotoma zonalis (Rohwer), F, Australia; Perga dorsalis Leach, F, Australia; Pergagrapta latreillei Leach, F/M, E Australia (BLM). Tenthredinidae: Euura sp., F, Sweden; *Nematus tibialis (Newman), F, Netherlands; N. salicis (L.), F, Netherlands; LMS Nematus sp., F, UK (LMS); Pristiphora pallidiventris Fall6n, F, Netherlands; Tenthredo sp., F, UK. Sirieoidea s.l. Siricidae: Eriotremex insignis Smith, F, E Indies (BLM); Eriotremex formosanus (Matsumura), F, Oriental (BLM); Tremex columba (L.), F, Nearctic (BLM); Tremex simulacrum Semenov, F, N. China (BLM); *Urocerus gigas (L.), F, UK; Xeris sp., F, UK; Xeris spectrum (L.), F, Australia (BLM); Xoanon mysta Semenov, F, E. Siberia (BLM). Xiphydriidae: Brachyxiphus grandis Philippi, F, Chili (BLM); Indoxiphia sp., F, Java (BLM); Moaxiphia decepta Smith, F, New Zealand (BLM); Xiphydria camelus (L.), F, UK (BLM); X. maculata Say, F, Canada (BLM); X. mellipes Harris, F, N. America (BLM); X. prolongata (Geoffroy), F, UK. Anaxyelidae: *Syntexis libocedrii Rohwer, 2F, USA. Cephoidea. Cephidae: Athetocephus madecassus Benson, M, Madagascar (LMS); Calameuta filiformis Eversmann, F, UK; Cephus pygmaeus (L.), F, UK; Hartigia sp., F, USA; Pachycephus smyrnensis Stein, M, no data (LMS); Trachelus libanensis Andre, M, no data (LMS); *T. tabidus (Fabricius), F, UK. Orussoidea. Orussidae: Chalinus haugi Buysson, F, W Africa (BLM); C. schulthessi Guiglia, F, S Africa (BLM); Guiglia sp., F, USA (BLM); Mocsarya metallica (Mocsfiry), F, Ceylon (BLM); M. syriaca Benson, F, M, Greece, Turkey (BLM); Ophrynopusfulvostigmus (Westwood), F, Amazon (BLM); O. wagneri (du Buysson), M, Argentina (BLM); Orussobaius wilsoni Benson, F, Australia (BLM); Orussonia depressa Riek, M, Australia (BLM); Orussus sp., F, Argentina; O. abietinus (Scopoli), F, Palaearctic (BLM); O. sayii (Westwood), F, Canada; 2F, 2M, E. Nearctic (BLM); O. thoracicus Ashmead, F, USA (BLM); O. unicolor Latreille, F, W Europe (BLM).



Trigonalyoidea. Trigonalyidae: Bareogonalos canadensis (Harrington), M, USA (BLM); B. scutellaris Cameron, sex unknown, N America (BLM); Labidogonalos flavescens Bischff., M, N America (BLM); L. sanctae-catharinae Schulz, F, Brasil (BLM); Nomadina smithi Westwood, M, Brasil (BLM); Orthogonalys pulchella (Cresson), F, USA; *Poecilogonalos costalis (Cresson), F, USA; Seminota depressa De Geer, sex unknown, S America (BLM); Trigonalis hahnii (Schulz), F, Netherlands; T. melanoleuca Westwood, F, M, Trinidad (BLM); Xanthogonalos fasciatus Brtni., F, Paraguay (BLM). Evanioidea. Evaniidae: *Evania appendigaster (L.), F, Wallis Is.; Evania sp, F, Argentina; Evaniella sp., F, Zimbabwe. Aulacidae: Aulacus striatus Jurine, F, UK; *Pristaulacus sp., F, no data. Gasteruptiidae: *Gasteruption sp., F, Zimbabwe; F, Rhodesia; G. assectator (L.), F, Sweden. Megalyroidea. Megalyridae: Carminator sp., sex unknown, no data (BLM); C. ater Shaw, ?, no data (BLM); Dinapsis turneri Waterson, sex unknown, no data (BLM); Ettchellsia piliceps Cameron, sex unknown, no data (BLM); Megalyrafasciipennis. Westwood, F, M Australia. M. longiseta Sz@ligeti, F, M, no data (BLM); M. rufipes Erichson, F, Australia (BLM); M. rufiventris; Sz6pligeti, F, M, no data (BLM); M. shuckardi Westwood, F, M, no data (BLM); M. testaceipes Turner, F, M, no data (BLM); M. wagneri, Fahringer, F, no data (BLM). Stephanoidea. Stephanidae: Diastephanus sp., F, Thailand; Foenatopus rubrugiceps Elliott, F, no data (BLM); Megischus maculipennis Westwood, F, no data (BLM); Neostephanus alluaudi Kieff., sex unknown, no data (BLM); N. oemidaphagus Benoit., F, no data (BLM); Parastephanellus spp., 2F, Brasil, Peru; Stephanus froggatti Cameron, F, Solomon Is. Cynipoidea. Cynipidae: Diplolepis rosae (L.), F, UK; Neuroterus sp., F, UK. Figitidae: gen. sp., F, UK; Alloxysta victrix Westwood, F, UK; Anacharis eucharioides (Dalman), F, UK; Figites anthomyiarurn Bouch6, F, UK; Melanips opacus (Hartig), M, UK Ibaliidae: *Ibalia leucospoides (Hockenwart), F, UK. Liopteridae: Liopteron sp., F, Malaysia. Ceraphronoidea. Ceraphronidae: Ceraphron testaceipes Kieffer, F, Germany. Megaspilidae: Dendrocerus sp., F, Poland; Dendrocerus carpenteri (Curtis), F, UK. Proctotrupoidea. Austroniidae: Austronia rubrithorax Riek, F, Australia (BLM). Diapriidae: Basalys sp., M, UK; Diphoropria nigricans (Dadd), F, Australia; Diapria conica (Fabricius), F, M, UK; Ismarus halidayi F6rster, F, UK; gen. sp. (Psilini), M, Kenya. Heloridae: *Helorus sp., F, UK Helorus ruficornis F6rster, F, Europe (BLM); H. rugosus Thomson, F, UK (BLM). Monomachidae: Monomachus sp., F, Brasil. Pelecinidae: *Pelecinus polyturator (Drury), M, Canada. Proctotrupidae: Codrus niger (Panzer), F, UK Roproniidae: *Ropronia sp., F, USA; R. garrnani Ashmead, F, N America (BLM). Vanhorniidae: *Vanhornia eucnemidarum Crawford, F, Canada. New family to be described: gen. sp., F, New Zealand. Platygasteroidea. Platygasteridae: Leptacis sp., F, UK. Scelionidae: gen. sp., sex unknown, Nepal; Trissolcus sp., sex unknown UK. Chalcidoidea. Chalcididae: Brachymeria sp., F, Kenya; Conura sp., F, Argentina. Eucharitidae: Orasema texana Gahan, F, USA. Eulophidae: gen. sp., F, Costa Rica, UK; Sympiesis sp., F, Costa Rica. Eupelmidae: Metapelma spectabile Westwood, F, USA Eurytomidae: Bephratelloides paraguayensis (Crawford), F, Trinidad. Leucospidae: Leucospis sp., M, USA. Mymaridae: gen. sp., F, Costa Rica; Acmotemnus luteiclava Noyes and Valentine, F, New Zealand (LMS); Acmopolynema nixoni Subba Rao, F, India (LMS). Perilampidae: Perilarnpus hyalinus Say, F,



Sweden. Tanaostigmatidae: Tanaostigmodes sp., F, Mexico. Torymidae: gen. sp., F, UK. Ichneumonoidea. Braconidae: Acanthodoryctes morleyi F, Australia (LMS); Amicrocentrum sp., F, Nigeria; Bracon fulvipes Nees, F, Netherlands; Callibracon sp., F, Australia (LMS); Charmon cruentatus (Haliday), F, Korea; Cotesiaflavipes Cameron, F, India; Homolobus sp., M, Malaysia; F, UK; Orgilus pimpinellae Niezabitowski, F, Netherlands; Petalodes sp., sex unknown, no data (LMS); Rhyssalus sp., F, UK; Syngaster lepidus Brull6, F, Australia (LMS); Trichiohelcon phoracanthae (Froggatt), F, Australia (LMS). Ichneumonidae: Arotes albicinctus Gravenhorst, M, Europe (BLM); A. amoenus, Cresson, F, USA (BLM); Deuteroxorides albitarsus (Gravenhorst), F, Europe; Earobia paradoxa Perkins, F, Switzerland (BLM); Enicospilus betanimenus Saussure, F, Angola (BLM); E. transvaalensis Cameron, F, Zambia (BLM); Habronyx albifrons Spinola, F, S Chile (BLM); H. heros Wesmael, F, Germany (BLM); Hieroceryx ascalaphoides Ceballos, F, W Africa (BLM); Ishigakia wahlburgi Roman, M, S Africa (BLM); Joppa dimidiata Brull6, F, S Africa (BLM); Lamachus eques (Hartig), F, UK; Metopius sp., F, Cameroun; Mesochorus testaceus Gravenhorst, F, UK (BLM); M. gracilentus Brischke, F, UK (BLM); Ophion sp., F, UK; O. ascus Gauld and Mitchell, F, W Java (BLM); O. facetious Gauld and Mitchell, F, N Sumatra (BLM); Orthocentrus excalibur Gauld, F, Australia (BLM); Osphrynchotus sp., F, Cameroun (LMS); Paracollyria clavator Thunberg, F, S Africa (BLM); P. flavipennis Cameron, F, S Africa (BLM); P. luteus Holmgren, F, S Africa (BLM); Paraphyscoteles celsus Tosquinet, F, S Africa (BLM); Phrudus milicornis Bridgman, F, UK (BLM); Pigmaeotus nitidus Bridgman, F, M, UK (BLM); SpiIopteron occiputatis Cresson, F, USA (BLM); Therion circumflexum, F, USA (LMS); Thyreodon sp., F, Florida (LMS); Xoridesfuligator (Thunberg), F, UK. Chrysidoidea. Bethylidae: Bethylus fuscicornis (Jurine), M, UK; Goniozus legneri Gordh, F, USA. Chrysididae: Adelphe anisomorphae Krombien, F, no data; Chrysis ruddii Shuckard, F, UK, Dryinidae: Chelogynus cameroni (Kieffer), F, UK; Prenanteon sp., M, UK. Plumariidae: gen. sp., F, Nambia. Sclerogibbidae: gen. sp., F, Nepal. Scolebythidae: gen. sp., F, no data. Vespoidea. Bradynobaenidae: gen. sp., F, Oman. Formicidae: Nothomyrmecia mac- rops Clark, M, Australia (BLM); Myrmecia simillima Smith, M, Australia (BLM); M. tarsata Smith, M, Australia (BLM). Pompilidae: Anoplius nigerrimus (Scopoli), F, UK; Arachnospila spissa (Schiodte), M, UK; Caliadurgus fasciatellus (Spinola), F, UK; Dipogon sp., sex unknown, no data (LMS); Pompilus rufus, F, UK (LMS). Rhopalosomatidae: Rhopalosoma sp., F, Costa Rica. Sapygidae: gen. sp., F, UK (LMS); Sapyga clavicornis (L.), F, Switzerland Scoliidae: Scolia hirta Schrank, F, Italy; gen. sp., M, Kenya. Tiphiidae: Tiphia femorata Fabricius, F, UK Vespidae: Odynerus reniformis, F, no data (LMS); Vespula consobrina (Saussure), F, USA. Apoidea. Apidae: Bombus lapponicus, F, UK (LMS); Melipona beecheii beechii (Bennett), F, Mexico. Sphecidae: Bembix sp., F, Kenya; Diodontus sp., F, UK; Passaloecus singularis Dahlbom, F, UK; Philanthus sp., F, Spain; Sceliphron sp., F, Canada (LMS).

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Hamuli in the Hymenoptera (Insecta) and their phylogenetic implications

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Transcript of Hamuli in the Hymenoptera (Insecta) and their phylogenetic implications