Consumption and utilization of a soyflour-wheat germ diet by larvae of the tobacco budworm parasitized by the tachinidEucelatoria sp

Abstract

The number ( $$\bar X$$ =2.4) ofEucelatoria sp. maggots that completed development in 4th- or 5th-instar larvae of the tobacco budworm (TBW),Heliothis virescens (F.), was significantly greater (P<0.05) than the number ( $$\bar X$$ =1.2) that completed development in 3rd-instar larvae. Maggot development time decreased with increasing number of maggots per host larva. It also decreased with advancing larval instars. The range was 6.9±1.1 days in early 3rd-instar TBW larvae and 5.0±0.8 days in early 5th-instar TBW larvae. Unparasitized 3rd- or 4th-instar TBW larvae consumed significantly more food than did similar aged larvae parasitized byEucelatoria sp., but larvae parasitized during the early 5th-instar consumed more food than did similar aged unparasitized larvae. Consumption by 4th- or 5th-instar larvae increased significantly as maggot densities increased from 1 to 3 per host larva, but decreased at a density of 4 or more maggots per host larva. Although body weight gain and consumption were both significantly reduced 48 and 120 h after parasitization of late 3rd-instar larvae (6 days old), the approximate digestibility (AD) value was significantly greater for parasitized than for unparasitized larvae. Unparasitized larvae were more efficient in converting digested food to body substance (ECD) than parasitized larvae, but the efficiency in conversion of ingested food to body substance (ECI) was similar for both parasitized and unparasitized larvae.