Laetilia coccidivora feeding on two cochineal insect species, Does the prey affect the fitness of the predator?

Dactylopius opuntiae (Hemiptera: Dactylopiidae) is a key pest of the prickly pear cactus in Mexico where the plant, and its phytophagous community, are native. It is also an introduced pest in Brazil and the Mediterranean basin. Amongst the phytophagous community of prickly pear in Mexico there is also Dactylopius coccus, the cultivated cochineal. This cochineal is used to obtain carminic acid as a natural dye, but it has also been reported as an invasive pest in Ethiopia. The most feasible control option for these insects is biological control, but whether their natural enemies develop well in both species is unknown. The aim of this work was to study the biology of the predator, Laetilia coccidivora (Lepidoptera: Pyralidae), when it was fed either D. opuntiae or D. coccus in the laboratory. The predator completed its development on both species. Carminic acid was at higher concentrations in D. coccus (8–25%) than D. opuntiae (2–5%), and feeding on D. coccus had negative effects on larval duration (16.7 vs. 22.0 days), developmental time (36 vs. 43.2 days) and survival rate of the predator (42.5 vs. 92.4%). Fecundity (22.7 vs. 12.9 eggs per female), net reproductive rate (R0 = 10.1 vs. 5.8) and intrinsic rate of increase (rm = 0.064 vs 0.041) were also diminished when L. coccidivora fed on D. coccus, compared with D. opuntiae. We discuss possible reasons for variation in predator fitness when fed on each prey type.