R. L. Pienkowski

Maternal environment and variation in ovariole number among populations of Melanoplus femurrubrum and M. scudderi scudderi

Ovariole number in univoltine populations of the grasshoppers Melanoplus femurrubrum (De Geer) and M. scudderi scudderi (Uhler) (Orthoptera: Acrididae) from Virginia was studied. Ovariole number in M. femurrubrum was found to vary among three geographic populations, and between years. Ovariole number did not vary between years in one population of M. s. scudderi. Ovariole number in M. femurrubrum was positively correlated with the mean length of the growing season at each site and precipitation during August‐September of the previous year (adult season of the maternal generation). In the laboratory, nymphal rearing temperatures did not affect ovariole number in M. femurrubrum, but it was found to be weakly correlated with egg size.

Insemination and sperm storage in the alfalfa weevil, Hypera postica (gyllenhal) (Coleoptera : Curculionidae)

Abstract Observations on the microanatomy of the aedeagus, bursa copulatrix, spermatheca, spermathecal duct, and spermathecal gland and on the activity of the sperm within the female alfalfa weevil, Hypera postica (Gyllenhal), were used as a basis for interpreting the mode of insemination and sperm storage. The aedeagus is inserted deeply into the bursa copulatrix during copulation. The endophallus protrudes from the aedeagus and attaches to the bursa copulatrix by sclerotized spines. Semen is deposited from the phallotreme into the bursa copulatrix near the entrance of the spermathecal duct. Muscle contractions by the bursa copulatrix and the spermathecal duct facilitate sperm in reaching the spermatheca. A nutritive secretion from the spermathecal gland permits sperm to maintain constant activity within the spermatheca. Stored sperm or a factor associated with sperm stimulates alfalfa weevil oviposition and causes other biological changes in the female.

Response of Three Populations of Liriomyza Trifolii (Diptera:Agromyzidae) to Topical Applications of Permethrin and Bifenthrin

Susceptibility to the pyrethroid insecticides permethrin and bifenthrin was determined for three populations of Liriomyza trifolii (Burgess) originally collected from commercial chrysanthemums in California, Florida, and Maryland. The Maryland population was significantly more resistant to both compounds than either the California or Florida population. Susceptibilities may have been affected by the number of generations populations were maintained as laboratory colonies.

THE INFLUENCE OF TEMPERATURE ON HOST ORIENTATION BY THE ALFALFA WEEVIL, HYPERA POSTICA1

The effect of temperature on the kinetic host orientation movements of mature adult alfalfa weevils, Hypera postica (Gyll.), was determined by mapping the movements of individual weevils in a closed arena in which the host odor source was just out of their reach. A reduced temperature resulted in a general reduction in activity, but an increase in the proportional efficiency of the kinetic orientation mechanism.

SEXUAL RESPONSIVENESS OF THE MALE ALFALFA WEEVIL, HYPERA POSTICA AS AFFECTED BY PRIOR CONTACT WITH OTHER ALFALFA WEEVILS1

Field‐collected alfalfa weevils exposed to eight different storage and testing conditions in the laboratory were evaluated for their reproductive behavioral responses. Males isolated in petri‐dishes underwent a build‐up and storage of sexual energy, allowing them to exhibit intense mating behavior toward either sex. When two males were stored together, they mounted each other and lost sexual energy, reducing subsequent matings. A male and a female stored together in a petri‐dish copulated frequently, and the male lost considerable sexual energy. Males which had been stored together or with females under moderately crowded conditions were sexually less active than non‐crowded males. Highly crowded males stored with females showed severely diminished libido during the evaluation period.