Changes in the fat body during the post-embryonic development of the predator Toxorhynchites theobaldi (Dyar & Knab) (Diptera: Culicidae)

Several studies have focused on understanding the biochemistry and morphology of the fat body of the hematophagous mosquito Aedes aegypti (L.) (Diptera: Culicidae). In contrast, few studies, if any, have focused on morphological characters of the fat body in other mosquitoes, especially non-hematophagous taxa such as the culicid Toxorhynchites. Larvae of Toxorhynchites prey upon the larvae of other mosquito species and are used in vector mosquito control. We investigated aspects of the fat body trophocytes, including the morphometric analyses of the lipid droplets, protein granules and nuclei, during Toxorhynchites theobaldi (Dyar & Knab) post-embryonic development. Following the body weight increase from larval stage L2 to L4, the size of lipid droplets within the trophocytes also increase, and are likely the result of lipogenesis. Lipid droplets decrease in size during L4 to the female pupal stage and increase once again during the period from newly-emerged to mature adult females. Protein granules are observed for the first time in female pupae, and their appearance might be related to protein storage during metamorphosis. The size of the nucleus of trophocytes also increases during larval development, followed by a decrease during metamorphosis and an additional increase as adult female ages. In conclusion, the morphology of the fat body of T. theobaldi changes according to the developmental stage. Our study provides for the first time important insights into T. theobaldi fat body development and contributes to understand this species biology.

Multiple queens in founding colonies of the neotropical ant Pachycondyla striata smith (Formicidae: Ponerinae)

In social insects, the typical mode of colony foundation occurs when a single queen is inseminated by a male and establishes a new colony, although we can find interspecific and intraspecific variations in queen number and queen-mating frequencies in a single colony. This study aimed to verify the queen number in Pachycondyla striata (Smith) colonies and to evaluate the level of aggressiveness among workers. We collected 14 colonies of P. striata. The behaviors of individuals from five multiple-queen colonies maintained in laboratory were studied by the method of scan sampling. In order to evaluate aggressiveness, dyadic encounters among heterocolonial and homocolonial workers were performed. The results showed that colonies of P. striata can have two or more mated queens (polygynous colonies) besides to monogynous ones (colony containing one queen). Because in polygynous colonies the number of workers was relatively low, such colonies could represent colonies in the foundation phase that characterize a pleometrosis state. In fact, ovarian development analysis from queens showed that the number of queens in the colonies seemed to be unstable. Despite a few cases of oophagy (egg cannibalism), social hierarchy among queens is unclear in comparison to other Pachycondyla species. In addition, aggressiveness increased with distance among nests. Nearby colonies (less than 1 m apart) showed a low level of aggressiveness, suggesting the presence of polydomy, that is, a unique colony can occupy multiple nests. Polygyny associated to polydomy in founding colonies may confer benefits on growth and dispersion of colonies in the studied environments.