Temporal assessment of molting in workers of Formosan subterranean termites (Isoptera: Rhinotermitidae)

Authors: KAKKAR, GARIMA - University Of Florida; CHOUVENC, THOMAS - University Of Florida; Osbrink, Weste; SU, NAN-YAO - University Of Florida

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/1/2016
Publication Date: 8/27/2016
Citation: Kakkar, G., Chouvenc, T., Osbrink, W.L., Su, N. 2016. Temporal assessment of molting in workers of Formosan subterranean termites (Isoptera: Rhinotermitidae). Journal of Economic Entomology. 109:2175-2181.

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 Formosan termite colonies were studied to compare molt frequency between termite workers in laboratory-reared juvenile colonies and foraging populations from field colonies. Chitin synthesis inhibitor (CSI) baits disrupt the molting process of workers that make up most of a termite colony. The time it takes the bait to kill the termites depends on how long it takes a poisoned termite to molt, which can provide insights into methods of reducing the time to eliminate a termite colony. It was determined that seasonal temperature changes are important. Results from a time lapse study on the foraging population of workers showed that at lower winter temperature it took almost 3x longer to molt (0.6% of workers molting per day) than that of workers at summer temperatures (2.2% of workers molting per day). Information from this study suggests time to molt is an important component of total time for eliminating colonies treated with CSI baits, and reduction in time lapse between two consecutive molts may reduce the time required for colony elimination.

Technical Abstract: Molt frequency of workers in laboratory-reared juvenile colonies and foraging population from field colonies of Coptotermes formosanus Shiraki was determined using planar arenas in laboratory. Given that, chitin synthesis inhibitor (CSI)-incorporated baits disrupt the molting process of workers that comprises the major population of a termite colony, temporal assessment of molting frequency in workers can give insights into potential methods of reducing the time to eliminate a CSI-baited colony. In our study the 10-d observation of juvenile colonies of C. formosanus suggested average daily molting incidence of workers in a colony is 1.7 6 0.3% (mean6SD). The results from a time lapse study on foraging population of workers showed that on average there is a 44-d intermolt period for second-instar workers molting to third instar and 45 d for third-instar workers molting to fourth instar. At low temperature (21 _C), molting frequency of workers (0.6% per day) was significantly lower than that of workers at 27 _C (2.2% per day). Information from this study suggests that time to molt is an important component of total time for eliminating colonies treated with CSI baits and reduction in time lapse between two consecutive molts may reduce the time required for colony elimination. Heterogeneous distribution of castes/instars and behaviors in the nest of Coptotermes formosanus Shiraki.