Comparative Life Histories of the Wolf Spiders Pardosa ramulosa and P. sierra (Araneae: Lycosidae)

Abstract

In the laboratory the early development of Pardosa sierra and P. ramulosa was similar. Carapace width and volume were measured. P. sierra is a larger spider with a total volume about three times as great as P. ramulosa. P. sierra matured in seven to nine instars in the laboratory while P. ramulosa took only six to eight instars. Maturity required an average of two months longer for P. sierra. In the field where the temperatures varied more and hence food intake per unit time was certainly less, these species took approximately an additional month to mature. The lengths of the instars varied, from 10 to 31 days, but there was no obvious regularity. This is similar to life cycle data for other spiders. In the field the number of individuals in catches was affected by weather con- ditions. For example, catches were smaller when the temperature was above 30 C and humidity was low, than when temperature was lower and humidity higher. Adults of both species were found at any month of the year, but the greatest pop- ulation of adults occurred in February and March. In both species populations and catches showed similar results. These species fit the category of spiders in which the instars are variable and the size is dependent upon the total length of the life cycle. The life histories of relatively few spiders are reported in the litera- ture. The purpose of this investigation is to add to this knowledge by reporting on several important aspects of the life cycles of Pardosa sierra Banks (1898) and Pardosa ramulosa (McCook 1894). Although both species are common in the Los Angeles area, P. ramulosa is found in a short grass environment while P. sierra lives among streamside boulders. The following features of the life cycle of each species were studied in detail: time of emergence from the egg sac, duration of each instar, carapace width of each instar, volume of individual spiders, field estimations of population size, and interrelationships between popula- tion size and fluctuations of air temperature and precipitation. 1 Present address: Route 2, Box 331F, Santa Fe, New Mexico 87501.