The Reproductive Capacity of the Larch Sawfly and Some Factors of Concern in its Measurement

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Abstract
Ovarian development and egg production in the larch sawfly, Pristiphora erichsonii (Hartig), were studied in the development of a method for measuring reproductive capacity for population studies. Most of the oöcytes are mature at the time of adult emergence but some mature in the following few days. Quantitative differences in foliage consumption during the larval stages have an appreciable effect on egg production but normal environmental temperature differences and exposure to flooding during the spring development period influence ovarian development only to a limited extent.Reproductive capacity can be determined by oöcyte counts of dissected adults of uniform age. The sample size necessary for estimates of various degrees of precision was calculated.Several size measurements have a significant correlation with the numbers of oöcytes produced. The regression of numbers of oöcytes on adult weight is of limited usefulness in the estimation of reproductive capacity. This is largely due to the individual variability in the extent to which fat body tissue is utilized in ovarian development particularly in the case of the larger adults.