Digger wasps Microbembex monodonta SAY (Hymenoptera, Crabronidae) rely exclusively on visual cues when pinpointing their nest entrances

Abstract

The ability of insects to navigate and home is crucial to fundamental tasks, such as pollination, parental care, procuring food, and finding mates. Despite recent advances in our understanding of visual homing in insects, it remains unclear exactly how ground-nesting Hymenoptera are able to precisely locate their often inconspicuous or hidden reproductive burrow entrances. Here we show that the ground-nesting wasp Microbembex monodonta locates her hidden burrow entrance with the help of local landmarks, but only if their view of the wider panorama is not blocked. Moreover, the wasps are able to pinpoint the burrow location to within a few centimeters when potential olfactory, tactile and auditory cues are locally masked. We conclude that M. monodonta locate their hidden burrows relying exclusively on local visual cues in the context of the wider panorama. We discuss these results in the light of the older and more recent literature on nest recognition and homing in insects.

Monarch butterflies memorize the spatial location of a food source

“…Based on our findings, it is unlikely that olfactory information was involved in the butterflies' spatial learning task, as they were able to target the same feeder even in the absence of sucrose (experiments 2 and 3). This suggests that monarch butterflies identified the feeder based on visual spatial information, which is in line with previous research that showed that insects, such as ants and wasps, rely on visual landmarks during orientation [11,14,66,67] and that olfactory cues play only a role in visually featureless environments, as shown for desert ants [68,69].…”

“…Here, we demonstrated that non-migratory monarch butterflies could relocate rewarding feeders by learning spatial information of visual landmarks. In line with many studies on hymenopterans [7,8,11,14,64,65], the butterflies' performance can best be explained by learning the spatial arrangement of multiple landmarks, i.e. the feeders.…”

“…This underlines the importance of visual landmarks for homing, and follow-up experiments demonstrated that this behaviour is independent from olfactory cues [14]. The advantage of memorizing spatial information from multiple landmarks becomes clear when considering the low spatial resolution of an insect eye, which makes the recognition of single landmarks difficult [11,[14][15][16]. Behavioural studies demonstrate that insects use memorized snapshots of the panorama [1,[16][17][18][19][20].…”

“…Especially, central-place foragers, such as bees, wasps and ants, demonstrate remarkable spatial memory feats [1,2,[4][5][6]. To relocate a spatial goal, many insects rely on either single salient landmarks or the spatial arrangement of landmarks [7][8][9][10][11][12]. In his pioneering experiments, Charles Turner observed the homing behaviour of burrowing-bees and concluded from the bees' responses to changes in the topography of the burrows' surroundings that visual cues are important for spatial memory [13].…”