Sarah McIntosh, 2014

University of Virginia

Does conopid parasitism cause bumble bees to collect less pollen and stay out overnight?

Bumble bees are important pollinator species for wild and economically valuable agricultural plants. While bumblebees are subject to many types of parasites, relatively little is known about behavioral changes caused by conopid fly (Diptera: Conopidae) parasites prior to the hostís death 10-12 days after infection. In order to determine if conopid infections reduce pollen return in Bombus impatiens individuals, bee pollen collection was compared with the presence and stage of parasite infection and overnight trip status in commercial colonies allowed to forage in the wild. Bombus impatiens individuals were affixed with RFID tags to provide data on foraging trip length and total time spent outside the colony while video monitoring provided a visual method of scoring pollen return. Conopid parasite status was then determined after a foraging period by monitoring these same individuals in captivity. The timing of infection was then determined at the conclusion of the study before video data is overlaid to look for behavioral changes associated with parasite status and overnighting. We found that parasitism is marginally related to decreasing pollen returns. We also found that overnighting behavior is not associated with conopid parasitism but rather trip day and also results in reduced pollen returns. Finally, a mathematical model based on observed mortality rates and parasitism rates showed that conopid infections reduce the lifespan of bumblebees substantially beyond that of other sources of mortality. These finding contradict previous studies that suggested that overnighting and conopid parasitism were related but we believe both have possible long-term implications for overall colony success.

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