Presentation of artificial diet: effects of composition and size of prey and diet domes on egg production by Orius insidiosus (Heteroptera: Anthocoridae)

Authors: Ferkovich, Stephen; VENKATESAN, THIRUVENGADAM - BIOTECHNOLOGY LAB, INDIA; Shapiro, Jeffrey; Carpenter, James

Submitted to: Florida Entomologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/15/2007
Publication Date: 9/1/2007
Citation: Ferkovich, S.M., Venkatesan, T., Shapiro, J.P., Carpenter, J.E. 2007. Presentation of artificial diet: effects of composition and size of prey and diet domes on egg production by Orius insidiosus (Heteroptera: Anthocoridae). Florida Entomologist. 90:502-508.

Interpretive Summary: The insidious flower bug feeds on thrips, aphids, mites, whiteflies and insect eggs and small larvae and is produced on natural hosts by over 33 commercial producers of beneficials. Scientists at the Center for Medical, Agricultural, and Veterinary Entomology, ARS, Gainesville, FL are developing an artificial diet for rearing the predator, but improvements still are needed as egg production by the females is inferior compared to predators reared on prey eggs. To determine if the way the diet is presented to the predators played a role in their acceptance of the diet, the scientists varied the size of the diet capsules and found that the insects fed more on diet presented in smaller capsules resembling prey eggs and subsequently produced more eggs. They also found that the size of the capsule did not matter in their acceptance of the diet if it was supplemented with protein extracted from prey eggs. This information provides a novel understanding of the factors involved in the acceptance of artificial diets by predators that will facilitate their mass production for use in augmentative programs.

Technical Abstract: Diet presentation is an important determinant in whether or not a predator accepts a diet. Artificial diet was presented to the insidious flower bug, Orius insidiosus (Say), encapsulated in Parafilm® in 10, 25 and 50 microliter volume domes (capsules with one flat side). Predators were also fed eggs of four species of lepidopteran eggs, Ephestia kuehniella Zelle , Plodia interpunctella (Hübner), Helicoverpa zea (Boddie), Spodoptera frugiperda (J. E. Smith), and Heliothis virescens (Fabrics), ranging in size from 19 ' 1.7 (mean'SD) nanoliters (nl) for P. interpunctella to 108 ' 21.3 nl for H. virescens eggs. Proteins were isolated from all five species of prey eggs by homogenization followed by removing the resultant lipid layer post-centrifugation, desalting the sample by column chromatography, lyophilizing the resulting proteins and testing the proteins as a diet supplement. Adult predators were placed on the various diets the third day after eclosion and allowed to feed for six days then were provided with an oviposition substrate for 24 hrs on day seven. Egg production by females feeding on the control diet capsules was highest on the 10 µl domes, decreased slightly on the 25 µl domes and was significantly reduced on the 50 µl domes. This effect of capsule size was negated on the 25 µl and 50 µl diet domes when the diet was supplemented with E. kuehniella egg protein. Egg production was highest and comparable on the E. kuehniella, P. interpunctella and H. virescens eggs and significantly less on S. frugiperda and H. virescens eggs and appeared to be related to the protein concentration rather than size of the egg. The concentration of protein ('g/mg fresh wt) in each egg species was 162, 122, 119, 89, 69 and 119, respectively for E. kuehniella, P. interpunctella , H. virescens, H. zea, and S. frugiperda, respectively. Eggs of E. kuehniella and P. interpunctella were the smallest, eggs of S. frugiperda were intermediate, and eggs of H. virescens and H. zea were the largest in size. Bioassaying the five egg protein extracts at similar protein concentrations in the large diet domes (50 µl) indicated that the H. virescens protein extract did not have significant activity in contrast to the E. kuehniella and P. interpunctella extracts which were active. This indicated that either the egg proteins were of superior nutritional value for reproduction in female O. insidiosus than those of the other species or that some other factor(s) associated with the protein extracts of these two species were responsible for the increase in oviposition rate we observed. Identification of the active substance in the E. kuehniella and P. interpunctella extracts should provide a better understanding of why predators fed diet supplemented with these extracts produce more eggs than predators fed diet supplemented with the H. virescens protein extract even though egg production by predators fed whole eggs of these three species is similar.