The cereal leaf beetle, Oulema melanopus (L.), has rapidly increased its numbers and range since it was discovered in Michigan in 1962. We have shown in this report that intraspecific density-dependent mortality is the major constraint on survivorship. We have attempted to quantify survival within a generation from the egg stage to the adult.Larval mortality varies among populations. Density-dependent mortality, caused by intraspecific competition, accounts for most of the variation of within-generation survival of the cereal leaf beetle in wheat and oats. Mortality in the first instar on oats and the fourth instar on wheat and oats is a linear function of the logarithm of total egg density. Establishment of the first instar on oats appears to become more difficult as density increases because leaf surface disturbance and interference with larger larva increases. Competition for food accounts for the increase in mortality of the fourth instar in both wheat and oats as density increases. Egg survival, survival of the first instar on wheat and in the second, third, and pupal stage in both crops are constants with respect to density. These constants can be expected to change with respect to other environmental parameters however, e.g. host variety, planting date, rainfall, etc.

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.

Can. Ent. 112: 1277Ent. 112: -1284Ent. 112: (1980 Mature Tetrastichus julis (Walker) larvae, which overwinter in the pupal cells of their dead cereal leaf beetle hosts, enter diapause in late summer. Diapause is maintained by warm conditions and short daylengths during late fall and early winter; it ends without a specific terminating stimulus. Subsequently the larvae remain in a state of postdiapause quiescence until soil temperatures rise above 9"C, the theoretical threshold (t) for postdiapause development. Emergence of the central New York population occurs when the parasites have accumulated 162 degree days (Do) of heat above 9°C. This K value is considerably lower than that previously reported for a population from Michigan.Our study provides the first experimental evidence that both temperature and photoperiod regulate the rate of diapause development in a parasitic insect. ResumeLes larves matures de Tetrastichus julis (Walker) entrent en diapause a la fin de 1'8ti et hivernent dans la cellule nymphale de leur h6te, le criockre des c6r&ales, aprks la mort de celui-ci. La diapause est maintenue par les conditions douces et les courtes photopinodes qui prevalent a la fin de I'automne et au debut de I'hiver; la terminaison de la diapause ne depend d'aucun stimulus sp6cifique. Par la suite les larves demeurent dans un Ctat de quiescent de postdiapause jusqu'a ce que la temp6rature du sol s'tleve au-dessus de 9°C seuil thdorique (t) du d6veloppement posterieur la diapause. Pour les populations du centre de I'btat de New York, I'bmergence se produit lorsque les parasites ont accumuli l'huivalent thermique de 162 degks-jours (Do) au-dessus de 9°C. Cette valeur de k est nettement inferieure a celle rapportee anteneurement pour une population du Micnlgan.Par cette etude, nous sommes les premiers demontrer expkrimentalement que la temperature et la photop6riode sont tous deux impliques dans la regulation de la vitesse du developpement chez un insecte parasitique en diapause.

No abstract

No abstract