Detailed social and phenological data collected from nesting aggregations exist for relatively few sweat bee species because nesting aggregations are rarely found in large numbers, even when local populations are highly abundant. This limits researchers’ abilities to assess the social status of many species, which in turn, limits our ability to trace the sequence of evolutionary steps between alternative social states. To address this problem, we demonstrate the utility of rehydrated, pinned specimens from pan trap and netting collections for generating inferences about the phenology and social status of a well-studied sweat bee species, Lasioglossum (Dialictus) laevissimum. A detailed comparison of phenology and reproductive traits, between pinned specimens and those in a previous nesting study, produced similar results for bivoltine foraging activity and eusocial colony organization typical in this species. We then used pinned specimens from monitoring studies to describe, for the first time, the foraging phenology and social behaviour of two additional Dialictus species, L. hitchensi and L. ellisiae. Both L. hitchensi and L. ellisiae each exhibited two peaks in abundance during their breeding seasons, indicating two periods of foraging activity, which correspond to provisioning of spring and summer broods. Differences in body size, wear, and ovarian development of spring and summer females indicated that L. hitchensi is most likely eusocial, while L. ellisiae is either solitary or communal. This study demonstrates that analyses of specimens obtained from flower and pan trap collections can be used for assessing the phenology and social organization of temperate sweat bees in the absence of nesting data. The phenological and social lability of many sweat bee species make them ideal for studying geographic and temporal variability in sociality, and analyses of pan trap collections can make these studies possible when direct observations are impossible.

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Published in Journal of Hymenoptera Research, v. 88.

Copyright Lyllian A.-J. Corbin et al.

This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

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journal_of_hymenoptera_research-088-017-s001.png (650 kB)
Supplementary material 1: Figure S1. Right forewing of an L. hitchensi female. https://doi.org/10.3897/jhr.88.73220.suppl1

journal_of_hymenoptera_research-088-017-s002.png (1016 kB)
Supplementary material 2: Figure S2. Scoring systems for mandibular wear (MW) and wing wear (WW). https://doi.org/10.3897/jhr.88.73220.suppl2

journal_of_hymenoptera_research-088-017-s003.png (421 kB)
Supplementary material 3: Figure S3. Scoring systems for ovarian development scores. https://doi.org/10.3897/jhr.88.73220.suppl3

journal_of_hymenoptera_research-088-017-s004.png (234 kB)
Supplementary material 4: Figure S4. Head width comparisons among weeks suggest a mix of social traits in L. hitchensi summer females. https://doi.org/10.3897/jhr.88.73220.suppl4

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