Robert G. Helgesen

A new role for temperature in insect dormancy: cold maintains diapause in temperate zone Diptera.

In early autumn, high temperatures terminate diapause in the alfalfa blotch leafminer Agromyza frontella; low temperatures maintain diapause. These responses subserve a thermally malleable dormancy and allow flexibility in the annual number of generations. The view that favorable conditions cannot reverse the course of diapause are contradicted by the data on A. frontella. A better understanding to life history studies and phenological models in insect pest management.

Estimation of recruitment rates and survival from field census data with application to poikilotherm populations

A procedure is developed for estimating population recruitment rates based upon field census data of mixed ages of the population. Such estimation is necessary when sampling newly recruited individuals is much more difficult than the sampling of more mature members of the population. The method utilizes a population dynamics model in conjunction with least squares estimation. A procedure for poikilotherm organisms is used to estimate oviposition and survival rates of Hypera postica.