Effect of Habitat Disturbance on Colony Productivity of the Social Wasp Mischocyttarus consimilis Zikán (Hymenoptera, Vespidae)

Social wasps are important elements of the fauna in a variety of environments, including human-modified environments. Evidence indicates that habitat quality affects the growth of  colonies of social wasps in urban environments. This study investigated whether the colony productivity of the social wasp Mischocyttarus consimilis Zikán (Hymenoptera, Vespidae) is affected by loss habitat quality in human-occupied environment. Nests of M. consimilis were collected in forest and urban environment between January 2010 and June 2011. Only nests that reached the decline stage were sampled. As productivity parameters, we measured the total number of cells constructed, total number of adults produced and dry mass of the nests. Productivity was significantly lower in urban than in forest environment for all parameters analyzed. Habitat quality is probably the principal factor that contributed to the lower productivity in urban environment. In this type of environment, particularly where the study was conducted, the vegetation adjacent to the nesting sites was composed predominantly of grasses. Such habitats may have limited resources available, especially those resources used by the wasps for feeding the immature, such as larvae of other insects. That result suggests that human degradation of habitats negatively affects the final productivity of colonies of social wasps

Opportunistic Strategies for Capture and Storage of Prey of Two Species of Social Wasps of the Genus Polybia Lepeletier (Vespidae, Polistinae, Epiponini)

The foraging activity in social wasps is complex behavior that involves the ability to locate and transport the resources necessary for the colony. The activity is opportunistic and generalist, sometimes adapting to the availability of the resources when the colonies are exposed to critical environmental conditions. The aim of this study was to evaluate the opportunistic behavior of two species of wasps of the genus Polybia for the capture and storage of prey in the form of flights of winged. Five colonies of Polybia occidentalis (Olivier) and two colonies of Polybia paulista (L.) were collected. Six of them contained stored winged of termites, and one contained winged of ants. The results indicated that these two species practice an opportunistic foraging strategy and are able to store large quantities of protein resources in their colonies

Variation in Chemical Composition of Cuticular and Nonpolar Compounds of Venom of Apoica pallens and Polistes versicolor

Although cuticular hydrocarbons and venom are important to the evolutionary success of social behavior, studies that investigated these compounds in tropical social wasps are rare. Thus, the aim of this study was to compare the cuticular chemical composition and the nonpolar portion of venom of Apoica pallens, a swarm-founding wasp and Polistes versicolor an independent-founding wasp. Gas chromatography coupled to mass spectrometry (GC/MS) technique was used. In the samples of A. pallens, 66 compounds were identified on the cuticle and 87 in venom, 13 are unique of the cuticle and 26 of venom. In the samples of P. versicolor, 85 compounds were identified on the cuticle and 60 in venom, 10 are exclusive of the cuticle and 5 of venom. The results show that, although they present different foundation types and organize in colonies with significantly different population number, the variation in chain length of compounds is relatively similar. In addition, in both types of samples of both species, the most representative class of compounds in content and number are the branched alkanes, which are recognized as the most effective during interactions between nestmates. However, there is greater similarity in content of shared compounds between samples of cuticle and venom of A. pallens, suggesting that because it is a species that is organized in more populous colonies, it may have a more elaborate signaling system based on volatile compounds of venom

Linear alkanes as a tool to evaluate intraspecific differences in social wasps

Cuticular hydrocarbons are found in the epicuticle of insects and act during interactions between nestmates in social insects. Among the classes of these compounds, branched alkanes stand out acting as flags during intracolonial interactions, therefore, varying significantly intraspecificaly. However, there is evidence that linear alkanes can also act as signals in these interactions and therefore would also be important to assess intraspecific differences in colonies of social insects. Thus, the hypothesis of this study is that linear alkanes can be used as a tool to establish intraspecific relationships in a species of social wasp. Linear alkanes of all developmental stages were evaluated from colonies of the species Mischocyttarus consimilis Zikán (Hymenoptera, Vespidae). 21 linear alkanes were detected, with the majority ranging from n-C26 to n-C33. There is significant variation between the compounds of all developmental stages, both from samples of different colonies and populations. Therefore, the results validate the hypothesis that variation in composition of linear alkanes can be useful to assess intraspecific differences in social wasps

You smell different! Temperature interferes with intracolonial recognition in Odontomachus brunneus

Intracolonial recognition among social insects is performed mainly by means of cuticular hydrocarbons (CHCs) that provide chemical communication, although their primary function is the avoidance of desiccation. Therefore, the ability to adjust to climatic variation may be related to the composition of CHCs. The hypothesis adopted in this work was that workers of the ant Odontomachus brunneus, when exposed to higher or lower average temperatures, change the CHCs composition, as a readjustment to the new conditions, and that this, in turn, leads to a change in intraspecific recognition capacity. To test this hypothesis, colonies of O. brunneus reared in the laboratory were subdivided into four groups. Two groups were kept at the same temperature, in order to assess the effect of isolation itself, while one group was kept at high temperature and another was kept at low temperature. Two groups were maintained at 25 °C, with no further conditions imposed. Subsequently, encounters were induced between individuals from these groups and from the high and low temperature groups, followed by the extraction of CHCs from each individual. The results indicated significant differences in recognition time and CHC composition between the high/low temperature groups and those kept at 25 °C. Antennation time during nestmate encounters was significantly longer for the groups submitted to temperature treatments (high and low), compared to those kept at 25 °C, suggesting recognition difficulty. In order to adjust to changing temperature conditions, O. brunneus undergoes changes in the composition of CHCs and in intraspecific recognition capacity

Deciphering the chemical phenotype in Atta laevigata (Smith, 1858) (Hymenoptera: Formicidae): A relationship between polymorphism and cuticular hydrocarbons

In the Attina subtribe the division of labor among workers is based on different tasks performed by morphological subcastes. Considering that cuticular chemical compounds play important roles as protection against water loss and mediates interactions between nestmates, and that studies on the cuticular chemical profile of ants of the genus Atta are still scarce, the aim of this study was to evaluate the relationship between morphological and chemical phenotypes in the subcastes of Atta laevigata (Smith, 1858) workers. The cuticular chemical composition of the different subcastes was assessed by Gas Chromatography coupled to Mass Spectrometry technique. The compounds found in the cuticle of the different subcastes had carbon chain size between 18 and 31 atoms, with higher content of linear alkanes in workers and soldiers and higher content of branched alkanes in gardeners and generalists, probably related to the type of tasks they perform in their colonies, since some workers perform more intra- or extranidal tasks in relation to others. The results show significant qualitative differences in the cuticular composition of the different subcastes, with a greater relationship between them according to the environmental restrictions that each subcaste is more subjected to due to the role played in the colony

Effect of Larval Topical Application of Juvenile Hormone on Cuticular Chemical Composition of Mischocyttarus consimilis (Vespidae: Polistinae) Females

Juvenile  Hormone  (JH)  is  considered  the  main  determinant  of  caste  in  social insects, though little is known about how this hormone acts in social wasps, especially the independent-founding species. The known relationship between JH titer and caste in the colony and we suggest a relationship among the effects of JH and the cuticular chemical profile. Therefore, this study aimed to test the hypothesis that topical application of JH to larvae of different instars alters the cuticular chemical composition of newly emerged females of Mischocyttarus consimilis (Zikán), influencing the dynamics of colony. Two techniques were used to evaluate the variation in cuticular chemical composition: Fourier transform infrared photoacoustic spectroscopy and gas chromatography coupled to mass spectrometry (GC-MS). Indeed, the application of JH did significantly alter the cuticular chemical composition of adult females that received treatment at the larval stage in comparison to control. The effects of JH were instar-dependent in that the results of topical application were significant when performed at third larval instar. Overall, these results add evidence that caste determination may, at least in part may be pre-imaginal in species of independent-founding social wasps

Anthropic action affects the cuticular chemical profile of social wasps

As a result of environmental change by anthropic action, animal species that inhabit these areas may suffer the effects of it on their phenotypes as a consequence of adapting to these conditions. In the case of social wasps, cuticular chemical compounds may be influenced, since these vary depending on genetic and environmental factors. However, few studies have investigated the synanthropic effects over the cuticular surface of social wasps. Therefore, the aim of this study was to investigate how cuticular compounds vary according to the different degrees of human activity and test the hypothesis that cuticular compounds of social wasps are affected by the level of anthropic activity in which their nests are found. Data on the cuticular chemical compounds composition of colonies of 3 species of social wasps were used along with the level of anthropization of their nesting sites in four municipalities in the state of Mato Grosso do Sul, Brazil. From the geographical coordinates of the sampling sites, the percentages of urban construction areas, agriculture, water body, vegetation and exposed land were calculated, and the nesting sites of the colonies were classified as more or less anthropized areas. The chemical profile was determined by extraction of cuticular compounds and analyzed by Gas Chromatography coupled to Mass Spectrometer (GC-MS). The results show that the cuticular chemical composition of the individuals of these species is affected by the level of anthropization in their nesting sites, with a qualitative and quantitative variation that must be tied not only to genetic differences, but, above all, to the local environmental conditions to which their colonies are subjected