1

Foraging Activity and Nesting of Swarm-Founding Wasp Synoeca cyanea (Hymenoptera: Vespidae, Polistinae)

by

Thiago Elisei1, Cleber Ribeiro Junior1, Daniela Lemos Guimarães1

& Fábio Prezoto1,2

ABSTRACT

This study describes the foraging activity in the swarm-founding wasp Synoeca cyanea and the substratum nesting used. From March 2004 to April 2005, 80 hours of direct observations were accomplished of different colonies of S. cyanea, in the Municipality of Juiz de Fora, Minas Gerais State, in south-eastern Brazil. The number of workers leaving and coming back to the nest, the temperature and the humidity were registered during the observations. The results of foraging activity in S. cyanea revealed a more intense activity during the hottest hours of the day (high temperatures and lower humidity). The mean of exits and returns /hour were 75.80 ± 71.94 (0-263) and 77.42 ± 72.42 (2- 264), respectively. Spearman’s test of correlation showed a positive correlation between the number of exits to forage with the temperature and humidity, but there wasn’t correlation with luminosity or the speed of the wind. The substratum used in the foundations by 37 nests of S. cyanea were tree trunks (86.46%), rocks (8.11%) and masonry (5.41%).

Keywords: social wasps, foraging behavior, nesting behavior, cli-matic factors.

INTRODUCTION

The genus Synoeca has five species present from Mexico to Argen-tina, and four are in Brazil (Richards 1978). The species Synoeca cyanea (Fabricius, 1775), a swarm-founding social wasp, popularly known as “marimbondo tatu”, is found in almost the whole country of Brazil. Their nests are composed of a single comb each whose cells are built directly on the substratum, covered by a protecting envelope, with an entrance in the superior part (Richards & Richards 1951). Some authors (Jeanne 1975, Richards 1978, Wenzel 1991) suggest that this architecture developed as protection against the predation pressure exercised by ants.

1Programa de Pós-graduação em Ciências Biológicas – Comportamento e Biologia Animal, Universidade Federal de Juiz de Fora, MG, Brasil. thiagoelisei@yahoo.com.br 2Departamento de Zoologia, Universidade Federal de Juiz de Fora, Campus Universitário Martelos, Juiz de Fora, MG, Brasil. Cep. 36036-900. fprezoto@icb.ufjf.br

2 Sociobiology Vol. 46, No. 2, 2005

There are few studies of the genus Synoeca, except the pioneer studies of Castellón (1980a,b; 1981; 1982) about reproduction and population dynamics, architecture and construction of the nests, and defensive and reproductive behavior.

Studies with Synoeca chalibea (Richards 1978) and Synoeca surinama (Richards 1978, Noll et al. 2004) demonstrated that these species do not present significant morphological differences among the castes. Even so, the study accomplished by Noda et al. (2003) for S. cyanea revealed that the queens are larger than the workers indicating a morphological differentiation among the castes.

The foraging behavior of the social wasps reflects an ecological interaction between the colony and the environment, representing important biological information. During development, the colony needs water for temperature control; wood pulp for the construction and repair of cells, peduncle and envelope; sugary substances for the feeding of larvae and adults and animal protein only for the feeding of the larvae (Höfling 1982, Prezoto et al. 1994, Silva & Noda 2000, Andrade & Prezoto 2001, Resende et al. 2001).

The foraging activity of most insects is influenced by heterogeneities present in the environment, like irregular soil levels, obstacles, gradi-ents, and predictable varying qualities such as temperature, humidity or light intensity (Bonabeau 1998). There are no works that describe the foraging activity of wasps of the genus Synoeca. Therefore the objective of this study was to analyze the foraging activity and the substratum nesting used by S. cyanea.

MATERIAL AND METHODS

The study was carried out from March 2004 to April 2005 in the Universidade Federal de Juiz de Fora (21º46’S; 43º21’W, altitude 800m), Juiz de Fora, Minas Gerais State, Brazil.

Eight observations were accomplished (Table 1), in different colonies of S. cyanea, all in the post-emergent stage (Fig. 1), according to the classification proposed by Jeanne (1972).

The data of the observations were registered by directly counting the number of workers that left and returned to the nest for foraging. The wasps were observed from 7:00 a.m. to 5:00 p.m., resulting in 10 hours of daily observations of each nest as proposed by Prezoto et al. (1994). The temperature (ºC) and humidity (%) was taken near the nests using a digital thermo-hygrometer (TemplecTM) at intervals of 30 minutes.

The number of individuals in the external part of envelope (= guards), the speed of wind and the intensity of light were recorded only three times (Table 1).

3 Elisei, T. et al. — Foraging Activity and Nesting of Synoeca cyanea

Spearman’s test of correlation was applied to verify the influence of the climate factors on the number of worker exits and the substratum used for nesting by 37 nests of S. cyanea were applied during the experiment.

Tab

le 1

. Mea

n, s

tand

ard

devi

atio

n an

d am

plitu

de fo

r tem

pera

ture

, hum

idity

, spe

ed o

f win

d, in

tens

ity o

f lig

ht, n

umbe

r of e

xits

and

re

turn

s of

wor

kers

per

hou

r and

num

ber o

f gua

rds

in th

e co

loni

es o

f Syn

oeca

cya

nea

stud

ied

(fro

m M

arch

/200

4 to

Apr

il/20

05)

in J

uiz

de F

ora,

Min

as G

erai

s S

tate

, Bra

zil.

Col

onie

s T

empe

ratu

re

Hum

idity

S

peed

of

Inte

nsity

of

Mea

n of

M

ean

of

Num

bers

of

mea

n (º

C)

mea

n (%

) w

ind

(m/s

) lig

ht

exits

re

turn

s pe

r gu

ards

pe

r hou

r ho

ur

1 24

.81

± 4

.42

60.6

7±20

.27

——

—

——

—

35.7

5±19

.59

40.2

5±23

.35

26

.4±1

3.65

(1

8.9-

35.1

) (2

4-89

) (9

-59)

(3

-77)

(1

3-58

)

2 23

.81

± 2

.68

79.8

4±8.

89

——

—

——

26

.92±

17.1

7 29

.23±

17.6

6

12.9

±14.

75

(2

0.9-

30.6

) (6

1-90

) (1

3-69

) (7

-57)

(2

-44)

3 24

.20

± 5

.32

73.2

7±19

.04

——

—

——

88

.30±

72.0

8 92

.07±

74.5

1 45

.6±6

.90

(18.

3-38

.4)

(30-

90)

(12-

211)

(1

4-20

9)

(33-

57)

4 28

.93

± 4

.65

64±1

7.93

—

—

——

—

205.

1±54

.62

217.

3±46

.21

——

—

(22.

5-39

.8)

(27-

88)

(109

-259

) (1

38-2

68)

5 22

.29

± 1

.51

83.6

2 ±

5.2

4 —

——

—

—

122.

6±71

.86

112.

8±61

.21

——

—

(20.

4-24

.9)

(73-

90)

(9-2

26)

(2-1

95)

6 27

.10

± 1

.82

57

.33

± 6

.71

0.55

± 0

.23

161.

38±1

82.6

0 66

.7±1

7.50

65

.1±1

8.05

—

——

(2

2.4-

29.9

) (4

6-74

) (0

.16-

0.99

) (1

7-57

6)

(38-

89)

(34-

88)

7 26

.52±

2.07

63

.23±

10.1

4 0.

41±0

.28

168.

61±1

82.2

7 29

±13.

61

30.9

±12.

06

——

—

(22.

1-29

.8)

(46-

80)

(0.1

1-1.

29)

(22-

645)

(1

1-47

) (1

4-51

)

8 25

.28±

1.56

63

.8±7

.04

0.44

±0.3

2 14

7.85

±116

.22

18.5

±11.

07

22.0

±10.

1 —

——

(2

2.6-

27.9

) (5

3-75

) (0

-1.0

5)

(19-

505)

(5

-43)

(9

-36)

4 Sociobiology Vol. 46, No. 2, 2005

RESULTS & DISCUSSION

The foraging activity started earlier than 6:30 A.M. and this activity stopped at the end of the afternoon at 6:30 P.M., with activity picking up between 10:00 A.M.and 16:00 P.M., coinciding with the hottest hours of the day. The mean of exits and returns /hour were 75.80 ± 71.94 (0-263) and 77.42 ± 72.42 (2-264), respectively.

The studies made of species of the genus Polistes and Mischocyttarus (Gobbi 1977, Prezoto et al. 1994, Giannotti et al. 1995, Silva & Noda 2000, Andrade & Prezoto 2001), wasps of independent foundation and the studies carried out for swarming wasps (Hofling 1982, Resende et al. 2001, Lima & Prezoto 2003, Paula et al. 2003), all from tropical areas, revealed a pattern of foraging activity of 6 A.M. to 7 P.M., with a larger activity registered for the concentrated period between 10 A.M. and 2 P.M., similar to the results found in the present study.

Temperature: During all observations the temperature measured daily varied from

22.29 to 28.93ºC (Table 1) and Spearman’s test of correlation showed

Fig. 1. Colony of Synoeca cyanea studied in the campus of “Universidade Federal de Juiz de Fora”, Juiz de Fora, Minas Gerais, Brazil.

5 Elisei, T. et al. — Foraging Activity and Nesting of Synoeca cyanea

a positive correlation between the number of exits to forage and the temperature (r = 0.45; p< 0.0001) (Fig. 2). But observations 4 and 5 (Table 1) happened in a colony of S. cyanea, that had the envelope destroyed because of strong rains. This event increased number of wasp’s exits in search of wood pulp, used for the repair of the envelope, revealing a strong correlation with the temperature (r = 0.80; p < 0.0001), when analyzed separately.

In moments when the sun shined directly on the nest, an increase occurred in the number of exits and returns, and of guards on the envelope vibrating their wings in order to ventilate the nest.

The studies done for swarm-founding wasps (Hofling 1982, Resende et al. 2001, Lima & Prezoto 2003, Paula et al. 2003) demonstrated that the workers ‘ exits of this species had the tendency to increase while the temperature was getting higher, similar to the results found in this study. Gobbi (1977) studied the foraging activity of Polistes versicolor (Olivier, 1791) and verified that the beginning of its activity depends on the temperature.

Humidity: The foraging activity increased when the humidity decreased.

Spearman’s test revealed the negative correlation with humidity and the number of exits (r = -0.45; p < 0.0001) (Fig. 3) and observations 4 and 5 (Table 1) when analyzed separately also revealed a strong correlation (r = -0.82; p < 0.0001), similar to the result found for the temperature.

Fig. 2. Foraging activity of a colony of Synoeca cyanea on 17th December2004, in relation to temperature, in Juiz de Fora, Minas Gerais State, Brazil.

6 Sociobiology Vol. 46, No. 2, 2005

This correlation between humidity and foraging activity was also observed for another species of swarm-founding wasps (Hofling 1982, Resende et al. 2001, Lima & Prezoto 2003, Paula et al. 2003), agreeing with this study.

During rainy days or days that proceeded rainy days, it was observed that individuals of S. cyanea sealed a leak of water with the mouth-pieces. The behavior began with the suction of water, present in the wall of the flooded nest, and this was expelled to the exterior of the colony (Fig. 4). O’Donnell & Jeanne (1993) related similar behavior by workers of Polybia occidentalis nominated as “suck water from nest”.

Intensity of lights: The luminosity was another factor that influenced the foraging

activity. Spearman’s test of correlation showed a positive tendency with the intensity of lights and the numbers of exits (r= 0.3544, p<0.0044) (Fig. 5).

Osgood (1974, after Lerer et al. 1982) suggests that Trigona hyalinata starts foraging in the morning influenced by the temperature, but the end of the activities in the afternoon depends on the luminosity. Giannotti et al. (1995) suggest that the luminosity is a factor that should influence the foraging activity in Polistes lanio too.

Although recorded in three observations, the data found in the present study suggest that the luminosity is correlated with the foraging activity of S. cyanea.

Fig. 3. Foraging activity of a colony of Synoeca cyanea on 17th December 2004, in relation to humidity, in Juiz de Fora, Minas Gerais State, Brazil.

7 Elisei, T. et al. — Foraging Activity and Nesting of Synoeca cyanea

Speed of wind: The speed of wind was the factor that influenced the foraging activity

least. Spearman’s test of correlation did not show a significant corre-lation between the speed of wind and the number of workers that left the colony to forage (r=0.2936, p<0.0195) (Fig. 6).

Although wind speed was not correlated with the number of foraging workers, we believe that the speed of the wind can influence the foraging activity. In certain moments of the observation, when the wind was more intense, the number of exits to forage decreased, then resumed as soon as the wind speed was reduced.

This work verified that foraging activity is most stimulated on days that there is more light and heat, and less humidity. According to

Fig. 4. Worker of Synoeca cyanea sucking water from nest after a rain.

8 Sociobiology Vol. 46, No. 2, 2005

Edwards (1980), the intensity of foraging activity varies according to colony age, season of the year, number and age of workers, number of larvae inside the nest or a combination of all these factors.

The medium number of guards per hour on the envelope of the colonies of S. cyanea studied was of 28.3 ±16.43 (2-58) (Table 1). During the observations it was possible to identify that in some moments of the day, when the sun shined directly on the nest, there was a great number of guards on the envelope, and some of these were involved in the ventilation. In the periods without direct incidence of sun, the number of guards decreased considerably, not registering any guards at some moments.

Paula et al. (2003) observed that the number guards in a colony of Parachartergus fraternus varied in agreement with the development phase: 12.35 individuals in the pre-emergence; 3.30 for the post- emergence; and 0.10 for the decline.

The foraging activity of S. cyanea is a result of a complex interaction among the phase of colony development, nutritional and climatic factors, characterizing the foraging behavior of this species in the Neotropical region. This shows the need of more studies to understand better this complex behavior.

Fig. 5. Foraging activity of a colony of Synoeca cyanea on 3rd March 2005, in relation to intensity of light, in Juiz de Fora, Minas Gerais State, Brazil.

9 Elisei, T. et al. — Foraging Activity and Nesting of Synoeca cyanea

Nesting behavior: The substratum used in the foundations of S. cyanea were tree

trunks (86.46%) (Fig. 1), rocks (8.11%) and masonry (5.41%). The plants used were of the following families: Arecaceae (37.37%); Leguminosa (50%); Cecropiaceae (6.52%); Araucariaceae (3.21%); Myrtaceae (3.21%); and Pinaceae (3.21%).

The substratum used by S. cyanea were flat surfaces, this implies that nest construction is facilitated once the species builds directly on the substratum. In trees that have too much bark, the foundations were in newer areas of the plant, free from this phenomenon. This construc-tion behavior is similar to that described for S. surinama by Castellón (1982b).

ACKNOWLEDGMENTS

The authors thank the Brazilian agencies Conselho Nacional de Desenvolvimento Científico e Tecnológico and Fundação de Amparo à Pesquisa do Estado de Minas Gerais for the financial support.

REFERENCES

Andrade, F.R. & F. Prezoto 2001. Horários de atividade forrageadora e material coletado por Polistes ferreri Saussure, 1853 (Hymenoptera, Vespidae), nas diferentes fases de seu ciclo biológico. Rev. bras. Zoociências, 3(1): 117- 128.

Bonabeau, E. 1998. Social insect colonies as complex adaptive systems. Ecosystems, 1: 437-443.

Fig. 6. Foraging activity of a colony of Synoeca cyanea on 13th March 2005, in relation to speed of wind, in Juiz de Fora, Minas Gerais State, Brazil.

10 Sociobiology Vol. 46, No. 2, 2005

Castellón, E.G. 1980a. Reprodução e dinâmica de população em Synoeca surinama (L.) (Hymenoptera, Vespidae). Acta Amazônica, 10(3):679-690.

Castellón, E.G. 1980b. Orientação arquitetura e construção dos ninhos de Synoeca surinama (L.) (Hymenoptera, Vespidae). Acta Amazônica, 10(4):883- 896.

Castellón, E.G. 1981. Alarma e defesa do ninho em Synoeca surinama (L.) (Hymenoptera, Vespidae). Acta Amazônica, 11(2):377-382.

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Noda, S.C.M., S.N. Shima & F.B. Noll 2003. Morphological and physiological caste differences in Synoeca cyanea (Hymenoptera, Vespidae, Epiponini) according to ontogenetic development of the colonies. Sociobiology, 41(3): 547-570.

Noll, F.B., J.W. Wenzel & R. Zucchi 2004. Evolution of caste in neotropical swarm-founding wasps (Hymenoptera: Vespidae; Epiponini). American Museum Novitates, 3467: 1-24

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Prezoto, F.P., E. Giannotti & V.L.L. Machado 1994. Atividade forrageadora e material coletado pela vespa social Polistes simillimus Zikán, 1951 (Hymenoptera, Vespidae). Insecta, 3(1): 11-19.

11 Elisei, T. et al. — Foraging Activity and Nesting of Synoeca cyanea

Resende, J.J, G.M.M. Santos, C.C. Bichara Filho & M. Gimenes 2001. Atividade diária de busca de recursos pela vespa social Polybia occidentalis occidentalis (Olivier, 1791) (Hymenoptera, Vespidae). Rev. bras. Zoociências, 3(1): 105- 115.

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