Support for maternal manipulation of developmental nutrition in a facultatively eusocial bee, Megalopta genalis (Halictidae)

Developmental maternal effects are a potentially important source of phenotypic variation, but they can be difficult to distinguish from other environmental factors. This is an important distinction within the context of social evolution, because if variation in offspring helping behavior is due to maternal manipulation, social selection may act on maternal phenotypes, as well as those of offspring. Factors correlated with social castes have been linked to variation in developmental nutrition, which might provide opportunity for females to manipulate the social behavior of their offspring. Megalopta genalis is a mass-provisioning facultatively eusocial sweat bee for which production of males and females in social and solitary nests is concurrent and asynchronous. Female offspring may become either gynes (reproductive dispersers) or workers (non-reproductive helpers). We predicted that if maternal manipulation plays a role in M. genalis caste determination, investment in daughters should vary more than for sons. The mass and protein content of pollen stores provided to female offspring varied significantly more than those of males, but volume and sugar content did not. Sugar content varied more among female eggs in social nests than in solitary nests. Provisions were larger, with higher nutrient content, for female eggs and in social nests. Adult females and males show different patterns of allometry, and their investment ratio ranged from 1.23 to 1.69. Adult body weight varied more for females than males, possibly reflecting increased variation in maternal investment in female offspring. These differences are consistent with a role for maternal manipulation in the social plasticity observed in M. genalis

The nesting biology of the sweat bee Halictus farinosus in California, with notes on H. ligatus (Hymenoptera: Halictidae)

Volume: 61Start Page: 122End Page: 13

The bionomics and immature stages of the cleptoparasitic bee genus Protepeolus (Anthophoridae, Nomadinae). American Museum novitates ; no. 2640

24 p. : ill. ; 26 cm.Includes bibliographical references (p. 24)."Protepeolus singularis was found attacking cells in nests of Diadasia olivacea in southeastern Arizona. The following biological information is presented: behavior of adult females while searching for host nests; intraspecific interactions of females at the host nesting site; interactions with host adults; oviposition; and such larval activities as crawling, killing the host, feeding, defecation, and cocoon spinning. In general, adult female behavior corresponds to that of other Nomadinae. Females perch for extended periods near nest entrances and avoid host females, which attack parasites when encountered. Females apparently learn the locations of host nests and return to them frequently. This may account for the high rate of cell parasitism (47%) in five nests excavated by the authors. Females oviposit in open cells and hide their eggs in the cell walls as do all Nomadinae. As this is considered to be an autapomorphic feature of the Nomadinae, Protepeolus and the other Nomadinae are believed to have had a common parasitic ancestor in spite of numerous biological dissimilarities. The first instar Protepeolus attacks and kills the pharate last larval instar of the host before consuming the provisions, a unique feature for nomadine bees. First and last larval instars and the pupa are described taxonomically and and illustrated. Brief comparative descriptions of the other larval instars are also given. Larval features attest to the common origin of Protepeolus and the other Nomadinae. Cladistic analysis using 27 characters of mature larvae of the Nomadinae demonstrates that Isepeolus is a sister group to all the other Nomadinae known from larvae, including Protepeolus, and that Protepeolus is a sister group to the Nomadinae excluding Isepeolus. Because of this and because larval Isepeolus and Protepeolus differ in numerous autapomorphic features, Isepeolus is placed in its own tribe, the Isepeolini, new tribe. Appended is a brief account distinguishing the four larval instars of the host, Diadasia olivacea"--P. [1]