Host Detection by Cuckoo Bumblebees: Choice Experiments Reveal Non‐Visual Cues Support Host Detection, but Accuracy Is Low

ABSTRACT

Cuckoo bumblebees must successfully locate and invade a colony of their host bumblebee species to achieve reproductive success. Past work has established the role of non‐visual cues in guiding cuckoo bumblebee host‐finding behaviour. However, a majority of these studies have used chemical extracts from host bumblebees rather than colonies that resemble what the cuckoo bumblebee would encounter in natural conditions. To further understand the role of non‐visual cues guiding cuckoo bumblebees and to quantify the accuracy with which cuckoo bumblebees find their hosts, we conducted a series of choice experiments with wild‐caught cuckoo bumblebees Bombus vestalis Geoffroy, 1785 and small lab‐reared colonies of their host, Bombus terrestris Linnaeus, 1758. Wild‐caught female cuckoo bumblebees were introduced to a flight arena containing four identical opaque boxes, each of which featured slits to release volatiles from bumblebees placed within. When only one box contained a small host colony, the cuckoo bumblebees were able to locate their hosts among the four boxes with 66.2% accuracy. When B. terrestris brood, workers and the queen were placed in separate opaque boxes, the cuckoo bumblebees did not show a clear preference among them but still avoided an empty control box. This is an initial step in understanding the accuracy of host detection in cuckoo bumblebees and the components of a colony attracting invasion.