Increased egg-laying in Orius insidiosus (Hemiptera: Anthocoridae) fed artificial diet supplemented with an embryonic cell line

The insidious flower bug, Orius insidiosus (Say) (Hemiptera: Anthocoridae), can be reared on an artificial diet absent of insect components, but yolk production is reduced and resultant rates of oviposition and egg production are poor. Supplementing the artificial diet with cells from an embryonic cell line, IPLB-(PiE) of Plodia interpunctella (Hübner), enhanced oviposition rates. Ovipositional rates were evaluated using a short 7-day bioassay. Cells were separated from Grace’s medium containing 10% fetal bovine serum, washed several times in Grace’s medium alone, and then homogenized before they were incorporated into the diet. In addition to the cell-supplemented diet, several control diets were also tested: diet supplemented with Grace’s medium alone, Grace’s medium with fetal bovine serum, and conditioned Grace’s medium (i.e., the medium the cells were cultured in). Adult predators were placed on the diets the third day after eclosion and allowed to feed for 6 days and provided with an oviposition substrate for 24 h on day 7. Egg production was significantly increased only in the cell-supplemented diet, a similar result that occurred when cumulative egg production was recorded during the life span of the females. Oviposition increased incrementally with the increase in concentration of cells added to the diet and was significantly better than control diet at 0.25 ml homogenized cells/1.2 ml diet (1.123 × 105 cells, 31 μg protein) to 1.0 ml cells/1.2 ml diet (1.86 × 106 cells, 124 μg protein). Although the cell line enhanced the rate of oviposition at a relatively low concentration of protein, we do not know if the protein or some other nutritional components of the cells were responsible for the increased oviposition rate. The cell line may be used to directly supplement the described diet for O. insidiosus and/or serve as a source of material that could simplify purification and identification of the cell component(s) responsible for stimulating oviposition. Additionally, the 7-day bioassay may be used to expedite identification of active fractions during chemical analysis of the cell line.