Mechanisms of reproductive suppression in female pine voles (Microtus pinetorum).

In co-operatively breeding birds and mammals, philopatric females are often reproductively suppressed. Many studies have focused on the functional significance of reproductive suppression, but further investigation of the mechanisms involved is required for a complete understanding of this process. This study investigated whether reproductive suppression in non-reproductive female pine voles (Microtus pinetorum) occurs as a result of lack of gamete maturation or lack of increase in LH. The behaviour of male pine voles was also examined to determine whether they show a preference for the mother versus her daughter, as lack of male stimulation may inhibit an increase of LH in daughter pine voles. Ovarian development and circulating LH concentrations were investigated in females housed with a prospective mate in the presence or absence of a parent. Maturation of gametes was not affected by the presence of a parent. In the presence of the mother, there was no increase in LH, as was observed in females housed with or exposed to a novel male. Males spent more time with mothers and possibly showed a preference for mating with the mother. These results are consistent with the contention that ovulation does not occur in female pine voles housed in the presence of their mother; however, it is not clear whether the lack of ovulation is caused by lack of stimulation from the male or suppression by the mother.

Statistical appraisal of the weight-wing length relationship of mosquitoes.

The relationship between wing length and body weight of mosquitoes was examined by comparing the fit of regressions using logarithmic and cubic transformations. A two-parameter line using a double logarithmic transformation provided the best fit, and we found no evidence to justify the use of wing length cubed as a transformation. Wing length was not directly proportional to body weight, but rather increased at a lesser rate than did body weight. Equations that predict body weight from wing length may not be an appropriate substitute for weighing mosquitoes, when studying the extremes of size in populations.

A new method for monitoring mosquito oviposition in artificial and natural containers.

A new method is described for the direct measurement of Aedes albopictus, Ae. atropalpus, Ae. triseriatus and Orthopodomyia signifera oviposition in artificial and natural containers. Seed germination papers were mounted on the insides of can-traps, tree holes and discarded tires to obtain a direct measure of mosquito oviposition. This durable paper substrate was removed weekly while minimizing the disruption of the oviposition habitat. After the germination papers were dried, the aforementioned mosquito eggs were hatched successfully and reared in the laboratory through the adult stage.

Penetration rate of two pesticide carriers at a large used-tire storage facility in Chicago, Illinois.

During August 1987, a large and concentrated infestation of Aedes albopictus was discovered on the property of a tire recapper and gasket manufacturer in Chicago, IL, in a densely populated urban environment. The infestation called for special abatement procedures because of the large number of tires and the varied ways they were stacked. An effective method for delivering pesticides into the cavity of each tire is described. Corncob granules, when applied to stacked tires, effectively penetrated this larval habitat at rates of 85% in column-stacked piles, 93% in random-stacked piles and an average of 95% in shingle-stacked piles. By comparison, gypsum pellet carriers sustained penetration rates of 37% in shingle-stacked piles and 87% in random-stacked piles.