TRIEPEOLUS BEHAVIOR - Preliminary notes

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Emergence dates 

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In 2025, male Triepeolus emerged at the nest site on April 8.  Males mated with females on the sandy trail of the nest area and disappeared by the third week of April.  Female Triepeolus remained flying through the second week of May.

 

Female Triepeolus behavior in nest area

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Brood parasites such as Triepeolus often locate ground nests fairly easily by searching for entrance holes to underground tunnels.  The Melissodes apicatus aggregation, however, proved unusually challenging to its brood parasites, because the nests lacked entrance portals. 

 

Female Triepeolus were unable to pinpoint nest locations without first observing a female host enter the sand.  Thus, despite the fact that the nest aggregation counted several hundred nests at its height, most of the female Triepeolus' time and activities focused on simply finding the nests. 

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Female Triepeolus patrolled the nest site from around 9:30 a.m. through noon each day, flying low to the ground in search of nest activity.  Occasionally, a female Triepeolus would drop to the ground to search for nest entrances and commence digging here and there in the ground.  The bee might dig so deeply that it submerged the front half of its body in the sand -- only to withdraw a few minutes later, having failed to find a nest entry portal.

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More commonly, Triepeolus females would wait for the arrival of a female Melissodes returning from a marsh, its legs laden with pollen.  When a Melissodes alighted in the nest area, a female Triepeolus would perch nearby (roughly 30-45 cm away), on the bare sand or a piece of plant detritus, watching as the Melissodes swiftly located its nest entrance, dug into the sand and disappeared.

 

​The Triepeolus would then wait for the host bee to emerge -- in some cases, the female pickerelweed longhorn would emerge in 15 minutes, but in others hours would pass without the host bee resurfacing.  A waiting Triepeolus was sometimes joined by other Triepeolus piggybacking on its discovery.  

 

If the host bee failed to resurface within half an hour, the attendant Triepeolus usually abandoned their vigil. No Triepeolus was ever observed entering a nest portal while the host was still inside.  

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If a Melissodes resurfaced soon after entering, the waiting Triepeolus would rush toward the host and stand a few centimeters from its exit point as it quickly emerged.  Sometimes the host bee would have to push the Triepeolus away while still exiting the sand. Other Triepeolus observing the commotion might then charge toward it to capitalize on the discovery of the exit location. The newcomers would vie with the Triepeolus already there, jostling to enter the nest first.  ​

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As soon as a host bee departed, any waiting Triepeolus would dig into the sand at the exit point -- much more slowly and less efficiently than the Melissodes.  A typical Melissodes apicatus could disappear into the ground in sixty seconds, but the Triepeolus labored as long as five minutes before disappearing into the passageway of sand loosened by the upward journey of the host.  After succeeding in entering the underground nest,  the Triepeolus female would remain hidden for five to ten minutes before reappearing.

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If two or more Triepeolus vied to dig into the entryway  simultaneously, one victor usually emerged, and a single bee would make the descent into the nest.  Less often, two bees would dig at once; this sometimes resulted in the entrance location being lost in the rivalry, and neither bee would find the correct entrance point.  

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Floral associations:

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No female or male Triepeolus were found feeding on plants in the vicinity of the nest site.  Nor were any Triepeolus found on pickerelweed in neighboring marshes.  

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Difficulties in identifying nectar sources for the Gainesville Triepeolus stemmed from the nest site's location in an area where few plants bloomed between March and late April.

 

During April, the predominant flowering plant was spurge nettle (Cnidoscolus stimulosus).  Slimleaf pawpaw (Asimina angustifolia) blossomed along the trail in late April and early May.  Neither of these plants, however, attracted bees.  Other flora found in limited quantities during April included frostweed (Crocanthemum corymbosum / C. georgianum), low prickly pear (Opuntia humifusa) and, in the third week of April, a  stand of blackberries (Rubus cuneifolius) set back 30 meters from the trail where the Melissodes aggregation was situated.

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From April 1 - May 5, no bees of any species were found feeding within 50 meters of the nest site, with the exception of three Lithurgopsis gibbosa on prickly pear.  This was despite weekly inventories of plants and searches for bee species feeding on flora.

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Neither Mitchell (1963) nor Rightmyer (2008) noted floral records for Triepeolus georgicus. Hall & Ascher reported finding Triepeolus georgicus on Asterceae in sandhill habitats -- specifically, one female on bushy aster (Symphotrichum dumosus), and one male on slender goldentop (Euthamia caroliniana), at Kanapaha Prairie, located 13 miles from Sweetwater Preserve; and one male on coastal plain honeycombhead (Balduina angustifolia) at Ordway-Swisher Biological station.  (Hall & Ascher 2014:  p. 9, table 3; Hall & Ascher 2010: p. 662, table 3).