Adaptive Traits of Riptortus pedestris Nymphs (Heteroptera: Alydidae) for Locating Host Plants

Abstract

Riptortus pedestris (F.) (Heteroptera: Alydidae) females oviposit not only on host plants but also on nonhosts, which may impose high costs on nymphs in terms of locomotion energy and time searching for host plants. Therefore, we hypothesized that second-instar nymphs have developed adaptive traits that help them access host plants, because the first feeding stage occurs during the second instar in this bug. We compared responses to the aggregation pheromone, relative leg lengths, and locomotion performance using a servosphere locomotion compensator as tests of physiological, morphometric, and behavioral traits, respectively, among the instars. We also investigated the effects of delayed feeding in the second instar on subsequent survival and development. Our results indicated that second-instar nymphs might have responded more sensitively to synthetic aggregation pheromone than other instars. Morphological measurements showed that second-instar nymphs had the longest relative leg length compared with other instars. The experiment using the servosphere revealed that second-instar nymphs had higher locomotion performance than did older nymphs, which may allow second-instar nymphs to walk a distance comparable to older nymphs, although their body size is much smaller. However, we did find that more than a 48-h delay in feeding after the first-instar molt decreased subsequent survival rates and that a later first-feeding led to a longer developmental period during the second instar. We concluded that R. pedestris nymphs have evolved various adaptive traits to enhance the probability of accessing host plants in response to the costly oviposition habit of adult females that lay eggs on nonhosts.

Responses of Second-Instar Male Nymphs of Four Mealybug Species (Hemiptera: Pseudococcidae) to Conspecific and Heterospecific Female Sex Pheromones

“…Few reports address the phenomenon of insect immature stages being attracted to the conspecific sex pheromone. Such attraction among insect was reported for the nymph stages of true bugs of three Heteropteran families (e.g., Aldrich, 1988;Nakajima et al 2010;Sant'Ana et al 1997;Yasuda and Tsurumachi 1995), and of the cockroach, Periplaneta americana L. *The heterospecific pheromone was that of P. citri; in P. citri tests the control pheromone was that of N. viridis **Means within a column followed by same letters are not significantly different (p>0.05); One-way Analysis of Attraction Intensity by each species and time period, comparisons for all possible pairs using Tukey-Kramer HSD (Schaller-Selzer 1984) . The former references cited are related to food searching behavior of the nymphs.…”

Fitness trade‐offs associated with oviposition strategy in the winter cherry bug, Acanthocoris sordidus

“…On the other hand, second instars of A. sordidus had enough locomotive ability to move at least 100 cm. Similarly, nymphs of R. pedestris and Palomena angulosa Motschulsky in the first feeding stage (i.e., second instar) have evolved high mobility to enhance their probability of reaching host plants in response to oviposition by females on non‐hosts ( P. angulosa : Wada & Hori, 1997; R. pedestris : Nakajima et al., 2010). Moreover, second instars may utilise chemical cues released by adult males and/or females to locate host plants, as the presence of adults on host plants (with the exception of when nymphs were released at a distance of 100 cm from potato plants with three males) increased the probability of nymphs reaching host plants by approximately 15% compared with plants with no adults.…”