Development of the gypsy moth (Lepidoptera: Lymantriidae) on Douglas-fir foliage

Survival of larvae, developmental time, consumption, live weights, frass pro-duction, pupal weights, and adult female ova production of the gypsy moth, Lymantriadispar (L.), were monitored in the laboratory for a comparison of performance between astandard synthetic diet and Douglas-fir, Pseudotsuga menziesii (Mirb.) Franco. Gypsy mothsurvival (96%), larval development (40 and 34 d at 22"C for females and males, respectively),and pupal weight (1,845 mg and 560 mg for females and males, respectively) on the standardsynthetic diet were very similar to data found in the literature regarding highly suitablediets. However, performance of the gypsy moth on Douglas-fir was indicative of a suboptimalhost. Survival of first instars on Douglas-fir ranged from 0 to 84%, depending upon temper-ature and foliage age. Development from first instar eclosion to pupation averaged 44.0 d(males) and 58.3 d (females) at 22''C. Male and female larvae consumed an average of 2,040.6mg and 6,136.1 mg dry weight of foliage, respectively. Frass production averaged 1,277.9mg (males) and 3,526.7 mg (females) dry weight. Values were low for nutritional indices ofefficiency of conversion of ingested food (4.5-4.9%) and efficiency of conversion of digestedfood (11.4-12.1%). Live pupal weights averaged 424.2 mg (male) and 1,249.8 mg (female).Females produced an average of 615.7 ova. The highest correlations among the developmentalparameters were between pupal weight : frass production and pupal weight : ova production.
KEY WORDS Insecta, Douglas-fir, gypsy moth, host suitability