Wilfrid Laurier University, Waterloo, Ontario - May 6 to 10, 2003

R. GARY CHIANG
Department of Biology, Redeemer University College, Ancaster, ON

A correlation between the number of larval plaques on the adult cuticle and blood-meal size in the insect, Rhodnius prolixus.

We reported previously that 50 to 100 µg of juvenile hormone (JHIII) applied on day seven after feeding to the last larval stage (L5) of Rhodnius results in adults with numerous larval plaques on their cuticle. These adults also ingested significantly more blood than controls. The present study reports that smaller doses of JHIII (1 to 2 µg) applied to L5 animals one day after feeding produced only a few larval plaques in a few animals, and that these animals ingested the same amount of blood as the controls. The difference in the ability of JH treated animals to ingest food can be explained by the difference in the flexibility of their cuticles, and this flexibility can be correlated with the number of larval plaques.

STEVE GREEN & R. GARY CHIANG
Department of Biology, Redeemer University College, Ancaster, ON

The use of the adult climbing apparatus in the insect Rhodnius prolixus as a bioassay for the effective dose of juvenile hormone (JHIII)

Between the claws and the first tarsomere of adult R. prolixus exists a soft, roundish, yellow structure that allows the adult to climb smooth vertical surfaces. This climbing apparatus, described in literature as the unguitractor, is absent in the larval stages. Topical application of JHIII to the dorsal cuticle of L5 females one day after ingestion of a blood meal has a number of dose dependent effects with smaller doses resulting in fewer juvenile characteristics in the adults. Among these effects is a significant decrease in the average size of the adult climbing apparatus coupled with impaired climbing ability. Using the size of this structure to determine of the minimal effective dose of JHIII, we found JHIII to be effective at levels as low as 0.4µg/animal.