IMPROVED FECUNDITY IN THE PREDATOR ORIUS INSIDIOSUS (HEMIPTERA: ANTHOCORIDAE) WITH A PARTIALLY PURIFIED NUTRITIONAL FACTOR FROM AN INSECT CELL LINE

A specific factor that stimulates egg production in the predator Orius insidiosis (Say) was earlier shown to be present in eggs of the Indian meal moth, Plodia interpunctella (Hübner). We investigated whether the embryonic cell line IPLB-PiE, derived from eggs of the Indian meal moth P. interpunctella also produces a specific factor that improves fecundity of the predator. We fractionated cells by preparative isoelectric focusing in a pH gradient of 3-10 and bioassayed the resultant fractions in test diets to determine their effects on egg production. Rates of oviposition were determined by placing adult predators on the test diets the third d after eclosion, allowing them to feed for 3 d, and then providing them with ovipositional substrates for 24 h on d 7. Six out of 20 fractions with isoelectric points between pH 5.2 and 7.3 had significant activity relative to the control diet. The nature of the factor(s) is unknown but corresponds to a partially purified fecundity factor from eggs of Ephestia kuehniella Zeller with an isoelectric point of pH 5 in an earlier study. The results indicate that the cell line, which was originally derived from embryos of P. interpunctella, has retained a differentiated function in culture by producing products similar to those produced in the P. interpunctella egg.