Note sur l’aire de distribution et l’importance du Dacnusa dryas, un parasite introduit au Québec pour lutter contre l’agromyze de la lyzerne (Agromyza frontella)

De 1978 à 1980, le Dacnusa dryas, un hyménoptère d'origine européenne parasitant les larves et les pupes de l'agromyze de la luzerne, Agromyza frontella, fut relâché successivement dans deux localités du Québec. Une étude détaillée de son aire de distribution effectuée en 1986 démontre que l'insecte s'est dispersé dans les douze régions agricoles du Québec. Suite à sa naturalisation, les populations d'agromyze ont diminué à des niveaux sous-économiques.

Size influences male mating success in the alfalfa blotch leafminer (Diptera: Agromyzidae)

Male size is an important parameter in mate choice for many species and has been associated with such female life-history parameters as increased fecundity or fertility and larger progeny (Phelan and Baker 1986; Savalli and Fox 1998, 1999; Brown 1999). In the alfalfa blotch leafminer, Agromyza frontella (Rondani), intraspecific larval competition may significantly influence the size of both males and females (Quiring and McNeil 1984a). The influence of female size on female reproductive success has been studied (Quiring and McNeil 1984b, 1984c), but to date, no attention has been given to the possible effects of male size. The objectives of this study were to determine if differences in male size, the result of intraspecific larval competition, affected male longevity and reproductive success, as well as various parameters of female reproduction.

Stereoselective syntheses of isomers of 3,7-dimethylnonadecane, a sex pheromone of the alfalfa blotch leafminer (Agromyza frontella (Rondani))

Two related stereoselective syntheses of 3,7-dimethylnonadecane, a sex pheromone of the alfalfa leafminer, are described to show that pulegone can serve as a useful starting material for the preparation of chiral aliphatic isoprenoid compounds. The schemes are designed to place the stereogenic center of pulegone at C.3 in one synthesis and at C.7 in the other so that the optical properties of the products can be compared with one another and with the values calculated using Brewster's rules. Key words: chiral hydrocarbons, stereoselective synthesis, pheromone, Agromyza frontella.

NOTE ON CYRTOGASTER VULGARIS WALKER (HYMENOPTERA: PTEROMALIDAE), A SECONDARY PARASITE OF THE ALFALFA BLOTCH LEAFMINER (DIPTERA: AGROMYZIDAE), WITH DESCRIPTIONS OF THE IMMATURE STAGES

Cyrtogaster vulgaris Walker, a pupal parasite of the alfalfa blotch leafminer, Agromyza frontella (Rondani), acts as a secondary agent as well. The adults, which deposit their eggs within host puparia, apparently do not discriminate between healthy leafminers and those parasitized by Dacnusa dryas (Nixon). The egg and larval cephalic structures of C. vulgaris are described and illustrated and the final-instar larval skins of the two parasite species are compared.

AN INTRASPECIFIC COMPETITION MODEL FOR THE LEAFMINER, AGROMYZA FRONTELLA (RONDANI)

A mathematical model was constructed to simulate the effect of intraspecific larval competition on the survival of Agromyza frontella (Rondani). It was shown that the probabilities of cannibalism and starvation can be expressed as functions of larval density and food availability (leaflet surface area), and that expected pupal weights can be determined from the amount of food available to the third-instar larva. Predictions were compared with data from laboratory experiments and field samples with excellent results.