Defensive use of an acquired substance (carminic acid) by predaceous insect larvae.

Larvae of two insects, a coccinellid beetle (Hyperaspis trifurcata) and a chamaemyiid fly (Leucopis sp.), feed on cochineal insects and appropriate their prey's defensive chemical, carminic acid, for protective purposes of their own. H. trifurcata discharges the chemical with droplets of blood (hemolymph) that it emits when disturbed; Leucopis sp. ejects the compound with rectal fluid. Ants are thwarted by these defenses, which are compared with the previously-described defense of a pyralid caterpillar (Laetilia coccidivora) that disgorges carminic acid-laden crop fluid. The defensive fluid of all three larvae contains carminic acid at concentrations spanning a range (0.2-6.2%) proven deterrent to ants. Many insects are known to appropriate defensive substances from plants. Insects that acquire defensive chemicals from animal sources may be relatively rare.