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 (r_m = 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.

仙人掌仙人掌（Dactylopius opuntiae）是墨西哥仙人掌植物的主要害虫，该植物及其食植物群落是墨西哥的本地植物。它也是巴西和地中海盆地的一种有害生物。在墨西哥的花椒的植物吞噬群落中，还有Dactylopius球菌（栽培的胭脂虫）。该胭脂用于获得作为天然染料的胭脂红酸，但在埃塞俄比亚也有报道称其为入侵性害虫。这些昆虫最可行的防治方法是生物防治，但尚不清楚它们的天敌在两个物种中是否发育良好。这项工作的目的是研究捕食时，捕食者Laetilia coccidivora（鳞翅目：Pyralidae）的生物学特性实验室中的D. opuntiae或D. coccus。捕食者完成了对这两个物种的开发。球菌中的氨基甲酸浓度较高（8–25％），比仙人掌菌（2–5％）高，饲喂球菌对幼虫的持续时间（16.7天比22.0天），发育时间（ 36天比43.2天）和捕食者的生存率（42.5比92.4％）。与以球菌为食的球孢梭菌相比，产卵率（每只雌性22.7比12.9个卵），净生殖率（R ₀  = 10.1比5.8）和内在增长率（r _m  = 0.064比0.041）也降低了。与D. opuntiae。我们讨论了以每种猎物为食时捕食者适应性变化的可能原因。