Biology and life history of Hyperaspis trifurcata feeding on Dactylopius opuntiae

Abstract

Hyperaspis trifurcata (Coleoptera: Coccinellidae) is a native predator of the wild cochineal scale, Dactylopius opuntiae (Hemiptera: Dactylopiidae) in North America. Here we have determined its life cycle and voracity when reared on first instar nymphs of D. opuntiae and estimated its population parameters using five diets based on different developmental stages of its prey: (a) first instar nymphs, (b) second instar nymphs, (c) young adults, (d) gravid adult females, and (e) a mixed diet which included all the developmental stages. The tests were conducted under laboratory conditions: 25 ± 2 °C, 60 ± 10 % RH and 12:12 (L:D) h. H. trifurcata developmental times were 5.9, 3.1, 3.6, 3.1, 8.9 and 11.4 days for the eggs, first, second, third and fourth instar larvae, and pupae, respectively. Overall there were 36.6 days from egg to adult emergence. Females consumed a mean of 5293 ± 361 first instar D. opuntiae nymphs during their lifetime, and there was no significant difference in developmental time between males and females. H. trifurcata could complete its life cycle when reared on any developmental stage of D. opuntiae. Nevertheless, the highest fecundity (237.4 ± 25.8 eggs) was obtained when they were fed the mixed diet, and the lowest fecundity and fertility were obtained when they were fed first or second instar nymphs, with a fecundity of 57.8 ± 10 and 140.5 ± 13 eggs and a fertility of 72 and 80 %, respectively. Moreover, the mixed diet increased the net reproduction rate (Ro = 112) and prolonged the generation time (T = 68.4 days) compared with females reared on first or second instar nymphs where Ro = 27.3 and 66.3 and T = 56.2 and 62.4 days, respectively. These parameters indicate that H. trifurcata has potential as a biological control agent of D. opuntiae.