After blood feeding on a host, bed bugs, Cimex lectularius, assemble in aggregation sites away from the host. Off-host aggregation is mediated by a combination of mechanical and chemical stimuli associated with bug feces. Partial antennectomies indicated removal of flagellomeres did not affect aggregation, but removal of the whole pedicel or its distal half significantly reduced (P<0.01) aggregation, suggesting that sensilla related to off-host aggregation occur on the distal half of the pedicel. Scanning electron microscopy (SEM) revealed that serrated hairs were distributed throughout the pedicel, but newly described smooth hairs were present mainly on the distal half, and a distinct patch of grooved pegs, smooth pegs and immersed cones was present on the posterior edge of the distal half of the pedicel in adults, but not in nymphs. Numbers of different types of sensilla increased significantly during metamorphosis from first instar to adult (P<0.05), but were similar between genders (P=0.11) and between females from a laboratory and field strain of bugs (P=0.19). Transmission electron microscopy (TEM) revealed that cuticular pores were present in the two types of pegs, indicating that the pegs have an olfactory function. The smooth hairs resembled gustatory sensilla previously described in Cimex hemipterus F. The existence of both olfactory and gustatory sensilla on the distal half of the pedicel suggests those sensilla may be the sensory basis of off-host aggregation behavior.
Bibliographical noteFunding Information:
We would like to thank Erin Brown, David Dotzauer, and Jinhda Praxayamoungkhoune from the Ecolab Research Center in Eagan, Minnesota and Gail Celio from the University of Minnesota Imaging Center in St. Paul, Minnesota for assistance with specimen preparation and imaging. We are also grateful to Aaron Rendahl from the University of Minnesota Statistical Center for statistical advice and Emory Matts from the Ecolab Pest Elimination Division for collecting field specimens. And finally, we would like to thank Dr. Peter Sorenson, Dr. Ralph Holzenthal from the University of Minnesota and two anonymous reviewers for helpful comments on an earlier version of this manuscript. This work was funded by Ecolab Inc., St. Paul, Minnesota ; University of Minnesota Agricultural Experiment Station projects MN-019 and MN-050; and the Marion Brooks-Wallace Research Fellowship for doctoral students in the University of Minnesota's Department of Entomology.
- Cimex lectularius
- Off-host aggregation