Does carminic acid concentration affect feeding preference of Hyperaspis trifurcata (Coleoptera: Coccinellidae) for two cochineal prey?

Carminic acid is a substance that probably works as a protection against predation. Its concentration differs between Dactylopius coccus and D. opuntiae. Then, we hypothesized that one specific predator, the coccinellid Hyperaspis trifurcata, would have a feeding preference for the species with lower carminic acid concentration. To test this hypothesis, choice tests were conducted using both species under laboratory conditions (25 ± 2 °C, 50 ± 20 % RH, and 12:12 h L:O). In the first assay, first instar nymphs of both species were offered to females of H. trifurcata. In the second gravid females, H. trifurcata consumed nymphs of the two species. The coccinellid showed no preference in the first instar nymphs; in such developmental stage, the carminic acid did not show an important difference between species. However, H. trifurcata preferred to feed on gravid females of D. opuntiae having a carminic acid concentration of 3 %, while such content was 23 % in D. coccus. Our results support the hypothesis that H. trifurcata prefers to feed on D. opuntiae instead of D. coccus due to the concentration of carminic acid, or some of its metabolic precursors.