Intraspecific Cuticular Chemical Profile Variation in the Social Wasp Mischocyttarus consimilis (Hymenoptera, Vespidae).

Chemical compounds present on the cuticle of social insects are important in communication, as they are used in recognition of nestmates and sexual partners as well as in caste distinction, varying according to several factors, such as genetic and environmental. In this context, some studies have explored the cuticular chemical profile as a tool for assessing intra- and interspecific differences in social insects, although few studies have investigated this in social wasps. This study aimed to assess the differences in cuticular chemical profiles among different geographic samples of the wasp Mischocyttarus consimilis Zikán. Our hypothesis was that environmental factors are decisive to compose the cuticular chemical profiles of colonies of these social wasps and that there are differences regarding the geographic distribution among colonies. We used Fourier Transform Infrared-Photoacoustic Spectroscopy (FTIR-PAS) to assess the chemical profiles of samples. Our results show that despite there are differences between the cuticular chemical composition of the wasps' samples from different populations, there is no significant correlation compared to the spatial distribution of the colonies nor with the environment. Thus, our hypothesis was refuted, and we can infer that in this species neither exogenous nor genetic factors stand out to differentiate the chemical signature of their colonies, but a combination of both.

Variation in Venoms of Polybia Paulista Von Ihering and Polybia Occidentalis Olivier (Hymenoptera: Vespidae), Assessed by the FTIR-PAS Technique.

Wasps are able to synthesize toxic compounds known as venoms, which form a part of a mechanism to overcome prey and also to defend their colonies. Study of the compounds that constitute these substances is essential in order to understand how this defense mechanism evolved, since there is evidence that the venoms can vary both intra- and interspecifically. Some studies have used liquid and gas chromatography as a reliable technique to analyze these compounds. However, the use of Fourier transform infrared photoacoustic spectroscopy (FTIR-PAS) to analyze the variations in venom's chemical profile has been proposed recently. This study evaluated whether the FTIR-PAS technique is effective for assessing the role of environmental factors on intra- and interspecific differences in the venom of the wasps Polybia paulista Von Ihering and Polybia occidentalis Olivier by FTIR-PAS. The colonies were collected in three municipalities of Mato Grosso do Sul, Brazil, in different types of environments. The results showed that the venoms of P. paulista and P. occidentalis differed significantly in profile. In addition, the intraspecific differences in the venom's chemical profile of P. paulista are related to the type of environment where they nested, regardless of the geographical distance between the nests. The FTIR-PAS technique proved to be reliable and effective to evaluate the variations in the venom's chemical profile in social wasps.

Chemical signatures in the developmental stages of Protopolybia exigua.

The chemical signature of social insects is very important for communication, and specific signs of each colony and its individuals are acquired throughout their development. This chemical signature can also be related to the composition of the materials employed during nest construction. Furthermore, the venom also contains important chemicals required for the maintenance of wasp colonies. Therefore, the objective of this study was to evaluate the chemical composition of the wasp Protopolybia exigua along its different development stages, including the nest substrate and the venom of adult worker at different ages. To achieve this, gas chromatography coupled to mass spectrometry was used. The results show that the chemical cuticular compounds present in different stages of development, and in the nest of P. exigua, are qualitatively similar, but quantitatively different, demonstrating that these compounds can be used as signals for the identification of co-specific individuals within the colonies. However, there was no significant variation in these compounds between different colonies, which may be related to the parental level between the colonies and due to them sharing the same resources. The non-polar compounds of the venom vary significantly according to the age of the workers, probably due to their different roles within the colony, and there was a clear increase in the complexity of the compounds as the wasps aged. Older wasps perform higher-risk activities, such as foraging, and therefore need to make more use of venom.

Morphological and Chemical Characterization of the Invasive Ants in Hives of Apis mellifera scutellata Lepeletier (Hymenoptera: Apidae).

Apiculture in Brazil is quite profitable and has great potential for expansion because of the favorable climate and abundancy of plant diversity. However, the occurrence of pests, diseases, and parasites hinders the growth and profitability of beekeeping. In the interior of the state of São Paulo, apiaries are attacked by ants, especially the species Camponotus atriceps (Smith) (Hymenoptera: Formicidae), which use the substances produced by Apis mellifera scutellata (Lepeletier) (Hymenoptera: Apidae), like honey, wax, pollen, and offspring as a source of nourishment for the adult and immature ants, and kill or expel the adult bees during the invasion. This study aimed to understand the invasion of C. atriceps in hives of A. m. scutellata. The individuals were classified into castes and subcastes according to morphometric analyses, and their cuticular chemical compounds were identified using Photoacoustic Fourier transform infrared spectroscopy (FTIR-PAS). The morphometric analyses were able to classify the individuals into reproductive castes (queen and gynes), workers (minor and small ants), and the soldier subcaste (medium and major ants). Identification of cuticular hydrocarbons of these individuals revealed that the eight beehives were invaded by only three colonies of C. atriceps; one of the colonies invaded only one beehive, and the other two colonies underwent a process called sociotomy and were responsible for the invasion of the other seven beehives. The lack of preventive measures and the nocturnal behavior of the ants favored the invasion and attack on the bees.

Cuticular signature in the development of Polistes versicolor.

Wasps belong to societies that are highly complex and diverse, especially considering social organization and parental care. They use chemicals in their daily communication, and act incisively in recognition of mates and non-nest mates, and can even identify individuals of different castes. In this study, cuticle composition was examined during the development of Polistes versicolor from the egg stage to adulthood, with the aim to assess changes in the chemical signature of the species, using gas chromatography. Linear alkanes and branched alkanes were identified that were important to distinguish the various developmental stages of P. versicolor. The variation in the linear alkanes and branched alkanes was quantitative, since most of them are present in all stages, with the exception of some linear alkanes that uniquely characterized the egg stage. At the egg stage, differences were predominant for linear alkanes C8, C24, C27, and C29. For the larval instars, there was a predominance of linear alkanes C8, C22 and C24 to C30. In the pre-pupae, pupae and adult stages, C8, C22, C24, and C26 to C30 showed a higher abundance during later developmental stages. The addition to branched alkanes increased their abundance from the egg (13.52%) to adult (22.96%) stages.

Fourier transform infrared photoacoustic spectroscopy as a potential tool in assessing the role of diet in cuticular chemical composition of Ectatomma brunneum.

The cuticular chemical composition plays a significant role in the recognition of nest mates in social insects, thus functioning as a chemical signature of the colony. The structure of cuticular chemicals is subject to interference from genetic and exogenous factors, including diet. In this study, various colonies of the Ectatomma brunneum ant were removed from their natural environment and housed in a laboratory to monitor the response of the cuticular chemical composition to dietary changes. Analyses were performed using gas chromatography and Fourier transform infrared photoacoustic spectroscopy, which has not been previously used for this type of analysis. The results indicate that this method is useful for analyzing biological and natural systems. We observed changes in the chemical signature with food traces in the first 30 days under feed control. Therefore, genetic information may not be the only criterion that can be used to describe the chemical signature of a species; environmental variations also influence recognition signals. Furthermore, these results reinforce the reliability of the Fourier transform infrared photoacoustic spectroscopy method.

Reproductive Status of Females in the Eusocial Wasp Polistes ferreri Saussure (Hymenoptera: Vespidae).

In the subfamily Polistinae, caste dimorphism is not pronounced and differences among females are primarily physiological and behavioral. We investigated factors that indicate the reproductive status in females of Polistes ferreri Saussure. We analyzed females from nine colonies and evaluated morphometric parameters, ovarian development, occurrence of insemination, relative age, and cuticular chemical profile. The colony females showed three kinds of ovarian development: type A, filamentous ovarioles; type B, ovarioles containing partially developed oocytes; and type C, long and well-developed ovarioles containing two or more mature oocytes. The stepwise discriminant analysis of the cuticular chemical profile showed that it was possible to distinguish the three groups of females: workers 1, workers 2, and queens. However, the stepwise discriminant analysis of the morphological differences did not show significant differences among these groups. The queens were among the older females in the colony and were always inseminated, while the age of the workers varied according to the stage of colony development.

Distinct linear hydrocarbon profiles and chemical strategy of facultative parasitism among Mischocyttarus wasps.

Insects use pheromones as a means of chemical communication. Pheromones act on individual receptors and produce specific behavioral or physiological responses that are fundamental to intra- and interspecific recognition. The objective of this study was to evaluate the interspecific differences among the linear hydrocarbon profiles of the cuticles of 3 wasp species of the genus Mischocyttarus. The chemical strategy that permits an interaction among 2 of these species was also examined about their hydrocarbon profiles. The cuticular hydrocarbons present on the abdomen of each individual were extracted with hexane in an ultrasonic bath and analyzed using gas chromatography with a flame ionization detector. The results suggested that the wasp species have distinct chemical signatures as the linear hydrocarbons of their cuticles. However, these signatures are more alike in those with similar morphological and behavioral aspects. These similarities facilitate an interaction of facultative parasitism observed among these species, in which the invaders acquire parts of the chemical signature of the host colony, possibly as a chemical strategy to increase the likelihood that an invader will be accepted by the females of a host colony. Both invader and host have their own chemical signature changed by the first contact between the species.

Age-related changes in the surface pheromones of the wasp Mischocyttarus consimilis (Hymenoptera: Vespidae).

One of the most important attributes that allowed the evolution and maintenance of sociality in insects is their ability to distinguish members of their own colonies. The capacity for individual recognition in social insects is mediated by chemical signals that are acquired soon after the adult emerges, and vary according to the tasks performed by individuals in their colonies. We determined the time when adults of the wasp Mischocyttarus consimilis acquire the chemical signature of their colonies, as well as the variation in the cuticular hydrocarbon profiles of the exoskeleton of individuals, according to their functions in the colony. The method used was Fourier transform infrared photoacoustic spectroscopy directly on the gaster of each individual. Young wasps take three to four days to acquire the colony's chemical signature, with a small change on the fifth day, when the cuticular hydrocarbon profile of the workers is more similar to that of the queens than that of the males, probably because they are of the same sex, but primarily because of the similarity of tasks executed by these two groups of females in the colonies.

Intra- and interspecific variation of cuticular hydrocarbon composition in two Ectatomma species (Hymenoptera: Formicidae) based on Fourier transform infrared photoacoustic spectroscopy

We have been able to discriminate different castes and sexes of ants in the same colony by measuring cuticular hydrocarbon levels with Fourier transform infrared photoacoustic spectroscopy, compared by canonical discriminant function analysis. We have now applied this methodology to various colonies of two species of ants of the genus Ectatomma in the Brazilian Cerrado. There were clear interspecific differences in cuticular hydrocarbons of these ants, with a small intraspecific variation. The differences between colonies were greater in E. brunneum than in E. vizottoi. Genetic differences among the colonies and species were well estimated by Fourier transform infrared photoacoustic spectroscopy and statistical analyses.

Comparative study of the cuticular hydrocarbon in queens, workers and males of Ectatomma vizottoi (Hymenoptera, Formicidae) by Fourier transform-infrared photoacoustic spectroscopy

Fourier transform-infrared photoacoustic spectroscopy was applied for the first time, to our knowledge, to distinguish different castes of an ant species. The method was applied directly to the abdomen of queens, workers and males of Ectatomma vizottoi ants, without any special sample preparation. The absorption bands of secondary amide and hydrocarbons were identified; using these as variables in a canonical discriminant analysis we found significant differences between the castes. Queens have a greater hydrocarbon content than do workers and males, which is related to their function in the colony. This technique can be used to analyze and distinguish small chemical differences in biological systems, even in opaque samples.