Behavioral Ecology and Sociobiology

, Volume 61, Issue 7, pp 1111–1120 | Cite as

Survival and productivity benefits to social nesting in the sweat bee Megalopta genalis (Hymenoptera: Halictidae)

  • Adam R. SmithEmail author
  • William T. Wcislo
  • Sean O’Donnell
Original Paper


Facultatively solitary and eusocial species allow for direct tests of the benefits of group living. We used the facultatively social sweat bee Megalopta genalis to test several benefits of group living. We surveyed natural nests modified for observation in the field weekly for 5 weeks in 2003. First, we demonstrate that social and solitary nesting are alternative behaviors, rather than different points on one developmental trajectory. Next, we show that solitary nests suffered significantly higher rates of nest failure than did social nests. Nest failure apparently resulted from solitary foundress mortality and subsequent brood orphanage. Social nests had significantly higher productivity, measured as new brood cells provisioned during the study, than did solitary nests. After accounting for nest failures, per capita productivity did not change with group size. Our results support key predictions of Assured Fitness Return models, suggesting such indirect fitness benefits favor eusocial nesting in M. genalis. We compared field collections of natural nests to our observation nest data to show that without accounting for nest failures, M. genalis appear to suffer a per capita productivity decrease with increasing group size. Calculating per capita productivity from collected nests without accounting for the differential probabilities of survival across group sizes leads to an overestimate of solitary nest productivity.


Per capita productivity Social flexibility Assured fitness returns Ecological constraints Halictidae Augochlorini 



ARS was supported by an AW Mellon Foundation Exploratory Award from the Smithsonian Tropical Research Institute (STRI) and the Organization of Tropical Studies (OTS), and research funds from WTW. S.O’D. was supported by NSF grant IBN-0347315. Victor Gonzalez participated through STRI’s “Behind the scenes” volunteer program and helped with constructing the glass-topped observation nests and making observations, while Gogi Kalka and Andre Riveros helped find nests in the field. Andrew Bouwma shared an unpublished manuscript and Simon Tierney and two anonymous reviewers provided helpful comments. The staff of STRI and the Organization for Tropical Studies provided logistical support. Research on BCI was conducted under scientific permit no. 75-99 from the Autoridad Nacional del Ambiente, in accordance with the laws of the Republic of Panamá, and research at La Selva was conducted under permission from MINAE in accordance with the laws of Costa Rica.


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Copyright information

© Springer-Verlag 2007

Authors and Affiliations

  • Adam R. Smith
    • 2
    Email author
  • William T. Wcislo
    • 2
  • Sean O’Donnell
    • 1
  1. 1.Animal Behavior Area, Department of PsychologyUniversity of WashingtonSeattleUSA
  2. 2.Smithsonian Tropical Research InstituteAPOUSA

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