Social organization of the eusocial wasp Mischocyttarus cerberus styx (Hymenoptera, Vespidae)

The present study was carried out under field conditions in Rio Claro, Southeastern Brazil. The following average life-spans of adults of Mischocyttarus cerberus styx were observed: queens 191.1 days, workers 14.0 days, and males 10.7 days. The short longevity of workers is attributed to the early foraging activity which was performed since the first week of adult age. The life table of the workers revealed high mortality rates during the first three weeks of life. Twenty-four behavioral categories were reported for these wasps and a comparative behavioral catalogue showed that the solitary foundresses (pre-emergence stage) are significantly more active than the queens (post-emergence stage) because they have to perform all the tasks for the nest maintenance. On the other hand, the queens were highly active even in the presence of the workers. The small number of individuals on the nest was the probable cause of the high activity of the queens in the post-emergence colonies. There was no clear division of tasks among workers according to their age (in weeks), so that most of the behavior categories were potentially performed by any worker of any age. Dead queens were replaced by their daughters.

Dominance hierarchy in different stages of development in colonies of the primitively eusocial wasp Mischocyttarus cerberus styx (Hymenoptera, Vespidae)

In primitively eusocial insect societies, reproductive division of labor is established by dominance-submission interactions which determine a linear dominance hierarchy. As previously observed for other species, in Mischocyttarus cerberus styx (Hymenoptera, Vespidae), the dominant female is the main egg layer. Most of her attacks were to the females directly beneath in the rank establishing a hierarchy. During the pre-emergence stage, the hierarchy was already defined and in the post-emergence stage, pre-male substage, the frequency of dominance interactions were strong but the hierarchy was still maintained by the first-ranked female. In the decline stage there were many neutral individuals which could be the reproductives of a new colony.

Nest architecture and population dynamics of the ponerine ant Ectatomma edentatum (Hymenoptera, Formicidae)

Twelve nests of Ectatomma edentatum (Hymenoptera, Formicidae) were collected from January to December 1996, in Rio Claro, SP, southeastern Brazil. This species excavates their nests up to 1, 10m deep, containing 2, 3, or 4 chambers with an entrance hole of up to 5mm diameter. Colonies with 104, 79, and 82 adult ants respectively were found in February, October, and November. These numbers decreased from March. Colonies with 21 and 16 adult ants were observed in May and July. The colonies' populations increased again in August. Immature stages were not seen January, February, and July, but there were many between March-April and September-November. There was no significant correlation between the number of individuals per colony and temperature or between the number of colonies and relative humidity and rainfall.

Division of labor in Ectatomma edentatum (Hymenoptera, Formicidae)

The behavioral division of labor between queens and workers of E. edentatum was investigated under laboratory conditions. Each behavioral category of both castes was described by direct observation of the ants in the colonies. The spatial position and the behavior of each individual were recorded. A colony ethogram was constructed to determine comparatively the behavioral repertory of the 2 castes. Most of the members of the colonies, including the queens, occupied the 2nd chamber, which also contained the immature stages. Forty-two behavioral categories were recorded for the workers, and 28 for the queens. The comparison of the behavioral repertory of the 2 castes revealed that ovipositing a fecundated egg is an exclusive behavior of the queens, while the workers showed 15 exclusive behaviors. Queens were never seen foraging out of the nest. Twelve behaviors were common for both castes. Polygynic colonies have only 1 female with full-developed ovaries, which is the main egg layer of the group, a feature defining the social organization of colonies of E. edentatum as a functional monogyny.

Temporal polyethism in workers of Ectatomma edentatum (Formicidae: Ponerinae)

In the present study, adult ants emerged from five nests kept under laboratory conditions were individually monitored in order to determine their longevity and observe their individual behavior in relation to age (temporal polyethism). Our results showed that most of the tasks related to colony maintenance were executed during the three first age intervals (comprising from 1 to 150 days of age), namely brood care, followed by grooming activities (self and allogrooming), nest maintenance activities (such as floor and nest inspection), and social related activities (antennating and food exchange among adults). Foraging activities were performed by ants in the higher age intervals.

Male behavior in colonies of the social wasp Polistes lanio (Hymenoptera, Vespidae)

Sixteen post-emergent colonies of Polistes lanio were studied while producing males in the course of the colonial cycle. Individually, they remained in the nest only 10.5 days (5-31, n=165). Twelve different male behaviors were observed: remaining immobile on the nest (82,8%), giving alarm (4,8%), flying out from the nest (2,4%), copulating on the nest (2,4%), being dominated (1,6%), self-grooming (1,2%), checking cells (1,2%), adult-adult trophallaxis (receiving food) (0,8%), larva-adult trophallaxis (0,8%), chewing prey and giving it to the larvae (0,8%), returning to the nest without food (0,8%), and fanning the nest (0,4%). In comparison to the behavioral repertory of females (28 items), they performed fewer tasks and remained immobile most of the time on the nest. Their behavior was largely related to self maintenance, but also included giving chewed prey to the larvae, giving alarm signals and fanning the nest.

Dominance hierarchy in different stages of development in colonies of the primitively eusocial wasp Mischocyttarus cassununga (Hymenoptera, Vespidae)

Seven colonies of Mischocyttarus cassununga were studied under field conditions at Universidade Federal de Juiz de Fora, MG, in southeastern Brazil: in pre-emergence, post-emergence and decline stages, during 145.8 hours. Dominance interactions among the females were quantified to verify the dynamics of succession in the social hierarchy of the colonies. Early pre-emergence colonies present more intense aggressive interactions than late pre-emergence ones, because the females are engaged in securing the role of main egg layer in the nest. In post-emergence (pre-male) colonies the dominance hierarchy is more defined and the frequency of dominance and subordination behaviors were lower than in pre-emergence stages: most of the agonistic behaviors are restricted to the first ranked females (potentially queens) and the subordinate individuals play the role of workers in the nests. In the post-emergence, post-male, and decline stages the hierarchy is still maintained by the aggressive behaviors of the 1st-ranked female but because the presence of males and future nest foundresses these interactions are not well defined in a linear way.

Population dynamics of Ectatomma brunneum (Hymenoptera, Formicidae) under laboratory conditions

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Daily activity resources collection by the swarm-founding wasp Angiopolybia pallens (Hymenoptera: Vespidae)

Angiopolybia pallens (Lepeletier, 1836) exhibited an intense activity at the beginning (6:00-7:00 a.m.) and end of the day (5:30-6:00 p.m.) (bimodal daily activity) and a low efficiency index in resources collection. The species also exhibited an equivalence relation in the items collected (nectar, prey and pulp) and a negative reaction to temperature and luminosity increasing, and reacted positively to an increase in the relative air humidity.

Nest site selection and flying capacity of neotropical wasp Angiopolybia pallens (Hymenoptera: Vespidae) in the Atlantic Rain Forest, Bahia State, Brazil

In order to evaluate the flying capacity and nest site selection of Angiopolybia pallens (Lepeletier, 1836), we made 17 incursions (136 hours of sample efforts) in Atlantic Rain Forest environments in Bahia state. Our data show this wasp prefers to nest on wide leaves of bushes and short trees (nests between 0.30 and 3m from the ground) placed in half-shady environments (clearings and shadowed cultivations). The logistic regression model using Quasi-Newton method provided a good description of the flying capacity observed in A. pallens (x 2 = 91.52; p≪0.001). According to the logistic regression model, the A. pallens flight autonomy is low, flying for short distances and with an effective radius of action of about 24m measured from their nests, which means a foraging area of nearly 1,800 m 2.

Male behavior of Mischocyttarus cerberus (Hymenoptera, Vespidae) during attacks on the nest by ants

The objectives of the present study were to verify if the males of the wasp Mischocyttarus cerberus participate in defense of the nest as they react to attack by ants, and to observe if they use chemical defense. First, wasps were stimulated with an empty pair of tweezers and a second stimulation was done with a pair of tweezers containing an ant, Camponotus crassus. The behaviors of the wasps were recorded and analyzed. The males can participate in defense of the nest, presenting some aggressive behaviors, even so, most of the time they ignore the stimulation, hide behind the nest and stay immobile.

Nest defense behavior against the attack of ants in colonies of pre-emergent Mischocyttarus cerberus (hymenoptera, vespidae)

The study was carried out at the UNESP Rio Claro campus (SP), where biotests consisting of simulated ant attacks were performed in colonies of Mischocyttarus cerberus. The behaviors of the wasps were recorded with a camcorder, for further analysis. This analysis was done using the Mann-Whitney U test and the Principal Component Analysis. In the pre-emergence development stage, colonies with a single foundress defend the nest only after the first larvae appear. When there are only eggs in the nest, the wasp abandons the nest. Before leaving, the wasp rubs its gaster against the nest, releasing the ant repellent secretion. When the nest contains larvae or larvae and pupae, the foundress defends the colony, vibrating its wings, pumping her abdomen and biting the ant.

Foraging activity of Protopolybia exigua (Hymenoptera, Vespidae) in different phases of the colony cycle, at an area in the region of the Médio São Francisco River, Bahia, Brazil

In this work, the foraging activity of Protopolybia exigua (de Saussure) was studied, aiming to verify the amplitude of the foraging time, the relation between the physical factors of weather (temperature, relative air humidity, luminosity and wind speed) and the daily activity of searching for resources, as well as to analyze the influence of the colony development phases and the number of individuals (adults and immatures) engaged in such activity. The study was carried out in two areas of the city of Bom Jesus da Lapa, Bahia, Brazil, during the period from January to June 2006, when the observation of 12 colonies of P. exigua was performed. The results revealed this species presented an amplitude of activity of almost 13 hours. There was an average of 44.4 nest exits and 37.6 returns a day by the nest workers and the Returns with Resources Index for this species was 93.5%. The foraging activity increased as of 10:01, and became more intense, with the peak from 1:01 p.m. to 4:00 p.m., when the highest temperatures (°C) and the lowest values of relative air humidity (%) were observed. The colonies that had a larger number of larvae presented a higher average number of trips to the field per hour (10.94) and the number of females in the colony tends to induce foraging activity. There were no differences between the numbers of nest exits by the workers regarding the three phases of colony development.