Molt-site fidelity in workers of Formosan subterranean termites (Isoptera: Rhinotermitidae)

Authors: KAKKAR, GARIMA - University Of Florida; Osbrink, Weste; MULLINS, AARON - University Of Florida; SU, NAN-YAO - University Of Florida

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/19/2017
Publication Date: 9/25/2017
Citation: Kakkar, G., Osbrink, W.L., Mullins, A., Su, N. 2017. Molt-site fidelity in workers of Formosan subterranean termites (Isoptera: Rhinotermitidae). Journal of Economic Entomology. 110: 1728-1735.

Interpretive Summary: The Formosan termite is the most devastating termite pest wherever it occurs in the world, and is well established in the south eastern part of the United States. Whole colonies with a king and queen were studied in large ant farms to determine the location of molting of Formosan termite workers in laboratory-reared colonies. It was determined that termite workers return to the main nest near the royal pair (king and queen) and brood (eggs and young termites) to molt. This is important because chitin synthesis inhibitor (CSI) baits kill termites by disrupting the molting process of workers that make up most of a termite colony. Other toxicants that kill near the bait stations cause repellency of other termites because of the decomposition of their bodies, thus preventing further poisoning of the colony. We have demonstrated that with CSI baits, the termites return to the nest to molt and die and do not contaminate the bait station with repellent dead termites. This provides an opportunity to accelerate such induced mortality using molting hormones or their mimics to speed up colony destruction.

Technical Abstract: Spatial assessment of molting in workers of Coptotermes formosanus Shiraki was conducted in laboratory-reared colonies using extended foraging arenas. Workers at pre-molt stage were found concentrated in nest or in a planar arena near the nest. However, molting individuals were found exclusively in the central nest and they stayed inside or near the central nest for at least 36 hous post-molting. Absence of pre-molt workers at foraging sites suggests that the workers have affinity to the nest for molting, and the second study on nest-fidelity evaluation suggested that the workers molt in proximity of eggs. The molting site fidelity by workers in a colony ensures that speeding up the time for mortality induced by chitin synthesis inhibitor (CSI) baits will not result in an inhibitory cascade of dead termites around the bait stations. Thus, speeding up the elimination of a C. formosanus colony using CSI baits with the addition of molt accelerating compounds will not lead to secondary repellency. Reasons for the molting-site fidelity amongst workers in a colony are discussed.