High-lipid prey reduce juvenile survivorship and delay egg laying in a small linyphiid spider Hylyphantes graminicola

Predatory mite Amblyseius orientalis prefers egg stage and low density of Carpoglyphus lactis prey

Amblyseius orientalis (Ehara) (Acari: Phytoseiidae) is an effective predatory mite for spider mite control on fruit trees in China. In recent decades, it has been produced massively at a commercial natural enemy producer, feeding on the storage mite Carpoglyphus lactis (L.). In the predator production process, the ratio of predatory mites to their prey was found to be critical for the population increase of A. orientalis in large-scale rearings. In this study, we investigated the predatory capacity of A. orientalis on various developmental stages of the prey C. lactis, and the effect of prey numbers on predator reproduction. The maximum predation rate of A. orientalis adults on C. lactis adults was 2.21 per day at the lowest density of five prey adults, and on C. lactis eggs it was 45.07 at the highest density of 60 prey eggs. The preference index C_i of A. orientalis on C. lactis eggs and adults was 0.4312 and - 0.9249, respectively, suggesting that A. orientalis preferred eggs to adults. Amblyseius orientalis could reproduce when it preyed on either eggs or deutonymphs of C. lactis. However, the fecundity of the predatory mites is not always proportional to the provided prey number. Higher density of prey deutonymphs resulted in lower fecundity, whereas more prey eggs resulted in higher fecundity of A. orientalis. Therefore, our study indicated that the choice of suitable density and developmental stage of prey can significantly improve A. orientalis production on a large scale.

The effects of prey lipid on female mating and reproduction of a wolf spider

As predators, the macronutrients spiders extract from their prey play important roles in their mating and reproduction. Previous studies of macronutrients on spider mating and reproduction focus on protein, the potential impact of prey lipid content on spider mating and reproduction remains largely unexplored. Here, we tested the influence of prey varying in lipid content on female mating, sexual cannibalism, reproduction, and offspring fitness in the wolf spider Pardosa pseudoannulata. We acquired 2 groups of fruit fly Drosophila melanogaster that differed significantly in lipid but not protein content by supplementing cultural media with a high or low dose of sucrose on which the fruit flies were reared (HL: high lipid and LL: low lipid). Subadult (i.e., 1 molt before adult) female spiders that fed HL flies matured with significantly higher lipid content than those fed LL flies. We found that the mated females fed with HL flies significantly shortened pre-oviposition time and resulted in a significantly higher fecundity. However, there was no significant difference in female spiders varying in lipid content on other behaviors and traits, including the latency to courtship, courtship duration, mating, copulation duration, sexual cannibalism, offspring body size, and survival. Hence, our results suggest that the lipid content of prey may be a limiting factor for female reproduction, but not for other behavioral traits in the wolf spiders P. pseudoannulata.