Ronaldo Zucchi

Increasing caste differences related to life cycle progression in some neotropical swarm-founding polygynic polistine wasps (Hymenoptera Vespidae Epiponini).

Morphological analyses of female wasps collected at different points in the development of the colonial life cycle showed that in Polybia occidentalis, P. paulista and P. scutellaris, caste differences progressively increase because larger queens appeared in more abundance in later stages of the colony cycle. Possibly, the mechanism can be of selective importance in the onset of the cyclical oligogyny, which is presently well documented in the life cycle of many swarm-founding polistine wasps. Males and uninseminated females with developed ovaries (intermediates) only occurred at the later stages of a colony’s developmental cycle.

The cuticular hydrocarbons profiles in the stingless bee Melipona marginata reflect task-related differences

Members of social insect colonies employ a large variety of chemical signals during their life. Of these, cuticular hydrocarbons are of primary importance for social insects since they allow for the recognition of conspecifics, nestmates and even members of different castes. The objectives of this study were (1) to characterize the variation of the chemical profiles among workers of the stingless bee Melipona marginata, and (2) to investigate the dependence of the chemical profiles on the age and on the behavior of the studied individuals. The results showed that cuticular hydrocarbon profiles of workers were composed of alkanes, alkenes and alkadienes that varied quantitatively and qualitatively according to function of workers in the colony.

Nestmate recognition in the stingless bee Frieseomelitta varia (Hymenoptera, Apidae, Meliponini): sources of chemical signals

Social insects use cuticular lipids for nestmate recognition. These lipids are chiefly hydrocarbons that can be endogenously produced or acquired from the environment. Although these compounds are already described as coming from different sources for different groups of social insects, nothing is known about the source of cuticular hydrocarbons in stingless bees. We used behavioural recognition tests and cuticle chemical investigation to elucidate the role of endogenous and environmentally based cues for nestmate recognition in the stingless bee Frieseomelitta varia. We found that although newly emerged workers present specific cuticle patterns according to their nest origin, these compounds are not used for nestmate recognition, since newly emerged workers are broadly accepted in different colonies. The cerumen used in nest construction played an important role in recognition behaviour. Twenty minutes of contact with foreign cerumen was sufficient to increase the rejection rates of nestmates and separate the groups of workers according to their chemical profile. On the other hand, tests of feeding on a common diet showed no effect on chemical cuticle pattern or recognition behaviour.

Morphological caste differences in the neotropical swarm-founding Polistinae wasps: Agelaia m. A. multipicta and A. p. pallipes (Hymenoptera Vespidae)

Distinct size dimorphism was found between queens (inseminated egglayers) and workers (uninseminated non egg-layers) sampled from mature colonies of Agelaia pallipes and A. A. multipicta. In both species, among 22 measured body parts queens were larger than workers in 17 characters. The Mahalanobis distance (D2) between castes was 122.74 in A. pallipes and 110.99 in A. A. multipicta, giving clear-cut evidence of caste separation, a conclusion which is strengthened by the absence of intermediate females. Comparisons with A. vicina and A. flavipennis demonstrated that morphological castes attributes are less developed in A. pallipes and A. A. multipicta.

Size and colony cycle in Polistes satan, a Neotropical paper wasp (Hymenoptera Vespidae)

Recent studies report that reproductive and non-reproductive roles of individuals can be associated with body size variation and/or physiological differences in many primitively eusocial wasps. This paper investigates the effects of the season on the body size and reproductive differences in Polistes satan. In pre-emergence colonies, inseminated females are significantly larger than subordinates for most of body measurements. Season has no effect on the differences related to the body size between inseminated females and uninseminated females from post-emergence colonies. However, most morphometric variables were significantly different between uninseminated females collected in distinct periods of the year. We suggest that seasonal variation may affect uninseminated females directly reflecting a flexible developmental programme in primitively eusocial wasps.

Caste-specific cuticular lipids in the stingless bee Friesella schrottkyi

While a queen control pheromone complex that inhibits worker ovary development has been described for honey bees, no comparable control pheromones have been identified for their sister group, the stingless bees. The aim of the present work was to search for possible control pheromones in the stingless bee Friesella schrottkyi. No volatile substances were found in the heads of queens that might serve as queen control pheromones. On the other hand, distinct differences were found between the cuticular substances of queens and workers. The major hydrocarbons were different between the two castes, and while queens contained methyl-branched alkanes and no unsaturated hydrocarbons, workers contained alkenes and alkadienes but no methyl branched hydrocarbons. Colonies deprived of a queen produced laying workers. Differences were observed in the cuticular patterns of laying workers and workers from a queen controlled colony.ZusammenfassungBei Honigbienen (Apis mellifera) kontrollieren die Königinnen die Fertilität ihrer Arbeiterinnen, indem sie mit einer Substanzmischung aus den Kopfdrüsen die Entwicklung der Arbeiterinneneierstöcke unterdrücken. Bei den Völkern von stachellosen Bienen ist es hingegen nicht bekannt, wie die Königinnen die reproduktiven Neigungen ihrer Arbeiterinnen kontrollieren. Im Rahmen unserer Untersuchungen über ein mögliches Dominanzpheromon der Königin bei stachellosen Bienen haben wir auch die kutikulären Substanzen und Drüsensekrete von Arbeiterinnen und Königinnen bei Friesella schrottkyi untersucht. Bei dieser stachellosen Bienenart produzieren die Arbeiterinnen keine Eier, solange die Königin anwesend ist; bei Abwesenheit der Königin entwickeln sie aber ihre Ovarien und legen männlich determinierte Eier. Vergleichende Analysen der kutikulären Substanzen von Königinnen, legenden Arbeiterinnen aus weisellosen Völkern und nicht legenden Arbeiterinnen aus einem weiselrichtigen Volk ergaben eindeutige Unterschiede zwischen diesen Gruppen. Bei allen Bienen wurden unverzweigte kutikuläre Alkane gefunden. Königinnen hatten zusätzlich Methyl-verzweigte Alkane, die weder bei den legenden noch bei den nicht legenden Arbeiterinnen nachgewiesen wurden. Beide Arbeiterinnen-Gruppen hatten aber unverzweigte Alkene und Alkadiene, die nicht bei den Königinnen gefunden wurden. Zusätzlich fanden sich bei Arbeiterinnen kleine Mengen an langkettigen Estern, die nicht bei Königinnen vorkamen. Nicht legende Arbeiterinnen wiesen die Kohlenwasserstoffe mit den größ-ten und Königinnen die mit den kleinsten Kettenlängen auf, während die Kettenlängen der legenden Arbeiterinnen dazwischen lagen. Das Kohlenwasserstoffmuster des Königinnenkopfes unterschied sich nicht von dem des Körpers. Bei Arbeiterinnen zeigten sich dagegen Unterschiede im Muster zwischen Kopf und Körper. So wurden kleine Mengen an volatilem Nonanal, Geranial und Neral sowie Octadecyl-Butyrat, Octadecyl-Hexanoat und Octadecyl-Decanoat ausschließlich in den Köpfen nachgewiesen. Es sind nun weitere Arbeiten geplant, um die Effekte von Einzelsubstanzen bzw. Substanzklassen auf das Verhalten von Arbeiterinnen zu überprüfen.

Nest materials and some chemical characteristics of nests of a New World swarm-founding polistine wasp, Polybia paulista (Hymenoptera Vespidae)

Nest material, nitrogen and amino acid composition of nests were examined in a New World swarm-founding polistine wasp, Polybia paulista. This wasp used minute vegetable chips, which were a dominant material, plant hairs, and mud and/or inorganic particles as nest building materials. A SEM observation and nitrogen and amino acid contents indicated that the amount of oral secretion used for construction and maintenance of the nests was quite small, compared with that used in Polistes nests. Such a small amount of oral secretion used for nest building is considered to be associated with their social organization (division of labor) and nest material. This study hypothesized that the amounts of oral secretion used for nest building are determined by an interaction among social organization, nest material and environmental factors, such as precipitation. Twenty-four amino acids were detected from protein in the nests of P. paulista, of which serine, glycine, alanine, valine, proline, aspartic acid and glutamic acid were major components. Amino acid composition of the protein in the nests of P. paulista differed distinctly from those of other so far known polistine and vespine wasps. The present result supports the view that amino acid composition of the protein in nests reflects phylogenetical relationships among wasps.

Bionomic notes on Pachysomoides sp. (Hymenoptera: Ichneumonidae), a parasitoid of the Neotropical social wasp Polistes satan Bequaert (Hymenoptera: Vespidae)

Although most polistine wasp species are found in the Neotropical region, mainly in Brazil, only a very limited number of South American parasitoids or parasites are known to exist. We assessed the frequency of a hymenopterous parasitoid, Pachysomoides sp. (Ichneumonidae, Cryptinae), in the nests of the Brazilian independent‐founding wasp Polistes satan and compared the rates of the parasitization of P. satan by Pachysomoides sp. between the dry (winter) and wet (summer) seasons. Pachysomoides sp. larvae were seen to feed on P. satan pupa and were found in both the upper and lower parts of the host pupal cell (ca. 10 individuals in each host pupal cell). Approximately one‐third of the pupal cells in the P. satan colonies were parasitized in the dry season, whereas there were no parasitized pupal cells in the wet season. Consequently, the rates of parasitization by Pachysomoides sp. were significantly greater during the dry season than during the wet season due to unknown reasons.

Nestmate recognition in a Neotropical swarm-founding wasp: no effect of seasonality on tolerance of alien conspecifics

Previous study revealed that the swarm-founding wasp Polybia paulista is accurately able to distinguish nestmates from non-nestmates in the summer. However, the risk of accepting alien intruders is considered to be low in winter colonies, and additionally brood production is limited in 30- 40% of colonies during the winter in this species. Thus, it is expected that colonies might lower their acceptance threshold and accept some conspecific wasps from alien colonies in winter. We conducted field experiments to examine tolerance of conspecific (nestmate and non-nestmate) females in winter. In contrast to our prediction, our colonies did not accept any individuals from alien colonies. We suggest that P. paulista exhibits the colony-specific acceptance threshold in winter, and colonies that produced brood in their nests may have raised the acceptance threshold even if the risk of accepting alien intruders is low in winter.

Effect of a foreign male’s age on acceptance into a conspecific colony in a Neotropical wasp

We conducted field experiments to examine whether young males of different age cohorts were accepted from alien colonies in the swarm‐founding wasp Polybia paulista. We showed, as for young females in other social wasp species, that newly emerged males were frequently accepted from alien colonies. Our study suggests that young males of P.u2003paulista acquire colony‐specific chemical odors shortly after emergence.