Relationship between body size and flying-related structures in Neotropical social wasps (Polistinae,Vespidae, Hymenoptera)

Body size influences wing shape and associated muscles in flying animals which is a conspicuous phenomenon in insects, given their wide range in body size. Despite the significance of this, to date, no detailed study has been conducted across a group of species with similar biology allowing a look at specific relationship between body size and flying structures. Neotropical social vespids are a model group to study this problem as they are strong predators that rely heavily on flight while exhibiting a wide range in body size. In this paper we describe the variation in both wing shape, as wing planform, and mesosoma muscle size along the body size gradient of the Neotropical social wasps and discuss the potential factors affecting these changes. Analyses of 56 species were conducted using geometric morphometrics for the wings and lineal morphometrics for the body; independent contrast method regressions were used to correct for the phylogenetic effect. Smaller vespid species exhibit rounded wings, veins that are more concentrated in the proximal region, larger stigmata and the mesosoma is proportionally larger than in larger species. Meanwhile, larger species have more elongated wings, more distally extended venation, smaller stigmata and a proportionally smaller mesosoma. The differences in wing shape and other traits could be related to differences in flight demands caused by smaller and larger body sizes. Species around the extremes of body size distribution may invest more in flight muscle mass than species of intermediate sizes.     

Self-organization of populations of polistine wasps (Hymenoptera,Vespidae, Polistinae)

In a natural population of Polistes dominulus (Christ) in the Black Sea Biosphere Reserve, Ukraine, the fluctuations of the number of nests founded were monitored in 1992–2008; the variations in the spatial and ethological structure of populations as well as in the colony organization patterns were examined. The highest indices of foundress fecundity (daily egg production, the foundress longevity after emergence of worker), colony productivity (the number of adults reared, the intensity of repeated cell use) and the efficiency of colony functioning (the degree of worker specialization and the mode of loyal or aggressive relationships between individuals) were characteristic of the population growth phase. In contrast, low indices were recorded during the peak and the decline phases. Transition to a more complicated social organization is favored by the self-organization process that accelerates the appearance of such interrelated features as a complex communication system, worker specialization, and their ability to perform complicated tasks. The study is focused on spatio-temporal processes in the population, using the body melanin patterns as markers of the social roles of foundresses. The changes observed in the population phenotypic structure are considered from the viewpoint of autowave processes. Analysis of the functional and numerical response of paper wasp parasitoids to changes in the host population density has shown that the regulating effect becomes noticeable only under such a concurrence of the life cycles of the parasitoid and the host when the larvae of the first cohort of workers become infested. The application of the concept of self-organized criticality used to describe complex systems with developed fluctuations results in a better understanding of population regulation in resocial insects.     

Pulp partitioning and worker specialization in polistine wasps (Hymenoptera,Vespidae, Polistinae)

The character of pulp partitioning was studied in three Palaearctic polistine wasps (Polistes dominula and P. gallicus in the Black Sea Biosphere Reserve, and Polistes nimpha in the Lugansk Nature Reserve, Ukraine) and in five Neotropical species (P. lanio, P. versicolor, Mischocyttarus injucundus, M. alfkeni, Metapolybia cingulata, and Protopolybia exigua in Trinidad). In independent-founding Polistes and Mischocyttarus species, all cases of pulp partitioning were connected with aggression on the part of the foundresses. An experimental increase of nesting density of P. dominula led to changes in the relative abundance of workers in the polyethic task groups. Some workers practically stopped hunting and switched over to pulp delivery; some of these workers possessed well-developed ovaries and were able to lay eggs. The experimentally removed part of the nest envelope in the swarm-founding wasp Metapolybia cingulata was restored only in colonies that included young workers. The specific features of nest building activity in independent-founding and swarm-founding polistine wasps are discussed.     

Metapolybia araujoi,a new species of swarming social wasp from the Brazilian Amazon rainforest (Vespidae: Polistinae)

A new species of Metapolybia, collected in Pará State, Brazil, by Adolph Ducke, in 1902, is described and comparative remarks are given.     

Richards' gland and associated cuticular modifications in social wasps of the genusPolybia Lepeletier (Hymenoptera,Vespidae, Polistinae,Polybiini)

Insectes Sociaux - O.W. Richards recently discovered an exocrine gland that opens on the fifth (penultimate) sternite of females of many species of polybiine wasps. Recent experimental evidence...     

Morphology and ultrastructure of the Dufour gland in workers of social wasps (Hymenoptera, Vespidae)

The Dufour gland in workers of vespine wasps appears as an unpaired tubiform gland that opens in close proximity to the sting base. The epithelial cells that line the central reservoir are characterized by apical microvillus-like projections and deep basal invaginations. Their cytoplasm contains a well-developed Golgi apparatus, numerous mitochondria, as well as strands of smooth endoplasmic reticulum. The Dufour gland duct occurs ventrally to the venom gland duct, and bends downward near the sting base to open in the dorsal vaginal wall. In this region, the duct is dorsoventrally flattened, and shows conspicuous bundles of parallel microtubules in the epithelial cells, that transmit the pulling forces of the myofilaments of the underlying muscular supply to the cuticle. This results in an active opening mechanism regulated by muscular contraction, while passive closure probably results from the return of the cuticular intima to a rest position.     

Abundance of wasps and prey consumption of paper wasps (Hymenoptera, Vespidae : Polistinae) in Northland, New Zealand

Polistine and vespine wasps were captured in Malaise traps in two fire-modified shrubland habitats of varying canopy height and composition at Lake Ohia, Northland, New Zealand. Prey consumption rates were calculated for the Asian paper wasp (Polistes chinensis antennalis) occupying these two areas of shrubland and a home garden in Whangarei, Northland. The sites were systematically searched for nests and wasp prey determined by intercepting foragers returning to nests. The Asian paper wasp predominated in the Malaise trap samples from the low- growing habitat while the German wasp (Vespula germanica) was more common in the taller vegetation type. The Asian paper wasp was more abundant than the German wasp in the samples in February and early March. Only four Australian paper wasps (Polistes humilis) and no common wasps (Vespula vulgaris) were caught. Asian paper wasps collected an estimated 15 000 prey loads per ha per season from one of the shrubland areas, and 478 000 prey loads per ha per season from the second area. These convert to estimates of 31 and 957 g per ha per season of invertebrate biomass removed by paper wasps from each habitat, respectively. The estimate for the garden site was 79 g per ha per season. Wasp nest densities varied between 20 and 210 nests per hectare. The biomass estimates are similar to average figures calculated for vespine wasps in scrubland and pasture. Both Asian paper wasps and Australian paper wasps preyed mainly on lepidopteran larvae. The cabbage white butterfly (Pieris rapae) was the most commonly collected species. Noctuid species were also well represented. Both male and female Asian paper wasps collected nectar in late March and early April.     

Uncovering head gland diversity in neotropical Polistinae wasps (Hymenoptera,Vespidae): Comparative analysis and description of new glands

Exocrine glands are involved in several wasp colony activities; however, the number of known glands in the Vespidae is rather low when compared to other social insect groups. The aim of this study is to survey the head of Neotropical social wasps and to provide a detailed comparative study of the glands found in the Polistinae. A total of 33 species distributed over 13 genera were studied with serial histological sections of the head, excluding the labiomaxillary complex. Additionally, the exoskeleton was explored using scanning electron microscopy looking for associated modifications. A total of eleven exocrine glands were observed, five are structures recorded for the first time for the Hymenoptera, three are new records for the Polistinae and three are previously known organs. The glands studied are: ocellar gland I, ocellar gland II, periocular gland, subantennal gland, hypopharyngeal gland, clypeal gland, posterobasal genal gland, ectal mandibular gland, mesal mandibular gland, intramandibular gland I, and intramandibular gland II. The widespread distribution of most of these glands suggests an origin prior to the evolution of the Polistinae. Our results highlight the importance of detailed morphological studies to unveil the significance of chemical communication in one of the most characteristic groups of social animals.     

Cryptically dimorphic caste differences in a Neotropical, swarm-founding paper wasp genus, Parachartergus (Hymenoptera: Vespidae)

Morphological differences in body shape between females of different reproductive conditions (in terms of insemination and ovarian development) were examined in two species of the Neotropical polistine genus Parachartergus: P. smithii and P. fraternus. The present study shows, for the first time, that non‐size‐based morphological divergence between queens and workers occurs in Parachartergus, an epiponine genus once believed to have little or no morphological caste differences. In the P. smithii colony examined, queens were significantly larger than workers in five of the eight body parts measured (head width, eye width, genal width, mesosomal length, wing length, first metasomal tergum width, and width and length of the second tergum), but the mean values of wing length and first and second tergum widths were not significantly different between them. The queen : worker size ratios tended to be greater anteriorly and smaller posteriorly, although the size ratio was greatest in second tergum length. Analysis of covariance (ancova ) with mesosomal length as covariate showed that queens had proportionally wider heads and narrower first terga than did workers. In the P. fraternus colony, size differences between queens and workers were not significant, and there was little or no difference in shape, but queens had significantly proportionally wider first terga than did workers.     

Behavioral mediators of cyclical oligogyny in the Amazonian swarm-founding wasp Asteloeca ujhelyii (Vespidae, Polistinae, Epiponini)

Summary In the Epiponini, queen number may vary from many to few during the colonial cycle. This cyclical oligogyny may be important for the maintenance of high genetic relatedness found in several taxa of epiponines. Even though queen reduction in accord with the colony cycle has either been demonstrated or inferred for many taxa, the factors responsible for queen number reduction remain largely unknown. In this study, behavioral interactions (queen-queen and queen-worker) were analyzed in Asteloeca ujhelyii. Conflicts among queens leading to queen elimination were more intense during colony establishment, and queens behavioral performances were significantly correlated with their potential reproductive capacity. Frequency of workers testing behaviors toward queens did not relate as a function of the colony cycle. Thus, it seems that in Asteloeca ujhelyii cyclical oligogyny is indeed behaviorally mediated.Received 16 January 2003; revised 1 June 2003; accepted 3 July 2003.     

Polymorphic microsatellite loci for the swarm-founding wasp Polybia paulista (Hymenoptera: Vespidae)

A polymorphic microsatellite locus was isolated and characterized from Polybia paulista, one of the most common polygynic, swarm‐founding social wasps in Brazil. Three other microsatellite loci for which the primer sets were originally developed in independent‐founding paper wasps also showed polymorphism in the size of amplification products in P. paulista.     

Observations onApoica pallens,a nocturnal neotropical social wasp (Hymenoptera: Vespidae,Polistinae, Epiponini)

Summary Colonies and nests ofApoica pallens in the llanos region of Venezuela range from small foundress nests to large mature colonies. Nests are sited on small diameter, near-horizontal branches in a variety of shrub and tree species. During the day, adult wasps cluster on the face of the nest in an array that seems to be determined by orientation to gravity; defense of the colony against parasitoids and ants by the resting wasps may be more a passive than an active behavior. Wasps fan their wings to cool the colony during the day, but no foraging for water accompanies the fanning behavior. Nightly foraging activity begins with the explosive departure from the nest of hundreds of wasps, most of which rapidly return. Moderate foraging levels early at night give way to very low foraging levels in pre-dawn hours. The period of moderate foraging may be extended for longer hours during increased moonlight. Foraging wasps collect arthropod provisions for larvae. Larvae produce a trophallactic saliva; adults engage in inter-adult trophallaxis; brood are cannibalized. During cluster formation prior to swarm emigration, adult wasps do not appear to scent-mark substrates such as leaves. Instead,A. pallens exhibits a calling behavior, unique among polistine wasps studied to date, in which the gaster is held rigidly away from the thorax and metasomal sternal glands are exposed. Swarms can emigrate during the day.A. pallens may incorporate absconding and colony relocation as features of its colony cycle in the highly seasonal llanos.