Differentiation of castes and aspects related to the colonial cycle of some wasps in Brazil. (Hymenoptera, Vespidae, Epiponini)

Author(s)

Mário Valentim Baio

• Document type: Doctoral Thesis
• Press: Ribeirão Preto.
• Institution: Universidade de São Paulo (USP). Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto (PCARP/BC)
• Defense date: 2002-08-12

Examining board members

Ronaldo Zucchi; Edilberto Giannotti; Nivar Gobbi; Fernando Barbosa Noll; Sulene Noriko Shima

• Advisor: Ronaldo Zucchi

Abstract

The Epiponini, neotropical social wasps (Hymenoptera: Vespidae), are important in the study of the evolution of social behavior because their colonies are polygynic (=many queens) castes present a wide range of morphological differences - from incipient castes to morphological distinct ones - and the occasional presence of intermediates forms of uninseminated females that present enough ovary development to lay eggs. Another aspect that calls attention is the cyclical decreasing in queen number until monogyny. Such fact has direct effect on the increasing of the genetic relationship among individuals in a population. Such phenomenon, the cyclical oligogyny, is extremely important to solve the interest conflicts between castes, as predicted by the Kin-selection theory. This work had the main purpose to identify the various types of morphological and physiological differences between castes, their variations and detail of the social behavior in different phases of the colonial life cycle. For such, morphological analyses and of ovary development studies, associated with multi-varied statistical analyses in six species (Brachigrastra augusti, Metapolybia docilis, Agelaia pallipes, Brachygrastra lecheguana, Pseudopolybia vespiceps and Protonectarina sylveirae) and observation of behaviors in two (Propolybia exigua and Metapolybia docilis) were performed. The results showed that just in Metapolybia docilis and Agelaia pallipes the intermediates are absent during the whole colonial life cycle. The number of queens varied in the analyzed colonies, in some cases, with a correlation in the different phases of the cycle. ln a general way, there is a clear work division among the groups tasks - Queens have function of oviposition and intermediates and workers of construction and maintenance of the nest, defense, and brood care. Intermediates of Protopolybia exigua lay eggs and ate them themselves. This fact can be related to the feeding of the colony\'s larvae. ln Metapolybia docilis the young workers (1-5 days) stay most of the time without activity and they are more subordinate to the queens; workers of stocking age (11-30 days) take brood care the maintenance and defense of the nest and; workers older (26-40 days) foraging. Finally, morphological considerations and the occurrence of intermediates and their role in different wasps taxa are discussed. (AU)