Kazumu Kuramitsu

The brown planthopper (Nilaparvata lugens, BPH) is a major pest in Asian rice ecosystems, and biological control by natural enemies is a key component of integrated pest management. Zoophytophagous mirid bugs, including Tytthus chinensis (Hemiptera: Miridae), play an important role as predators of BPH eggs and nymphs in Thailand. However, little is known about the potential of insectary plants to support the performance of T. chinensis. In this study, we evaluated the effects of Tecoma stans nectar on the longevity and reproductive development of T. chinensis under laboratory conditions. Adult longevity was compared among four feeding treatments: dry cotton, wet cotton, BPH eggs, and T. stans flowers. In addition, ovariole development was assessed under five feeding regimes combining BPH eggs and/or T. stans flowers. Access to T. stans nectar significantly extended adult longevity compared with the no-food treatments, and no significant difference in longevity was detected between predators provided with T. stans nectar and those provided with BPH eggs. Females provided with BPH eggs showed clear ovariole development, whereas those provided with T. stans nectar alone showed limited ovariole development. These results suggest that T. stans nectar may serve as an alternative food resource that supports adult survival, while access to prey appears to play an important role in reproductive development under the conditions tested. These laboratory findings support further evaluation of T. stans as a potential insectary plant for rice agroecosystems.

A new species of euphorine parasitoid wasp, Perilitus mahout Fujie sp. nov. from Japan was discovered by rearing adult Episomus turritus Chevrolat, 1863 (Coleoptera: Curculionidae). This is the first report of an adult parasitoid of Episomus turritus.

Strepsipterans are endoparasitic insects that parasitize hosts belonging to seven insect orders. They develop inside the host body, and adult males emerge to become free‐living. To date, male emergence has been observed only in the families Mengenillidae, Xenidae and Elenchidae (Order Strepsiptera), which parasitize silverfishes, hornets and planthoppers, respectively. In these cases, emergence sites on host bodies are exposed. However, in some strepsipterans, males emerge from the arthrodial membrane on the dorsal side of the abdomen, which is covered by the host's wings. Such emergence behavior has not been reported previously. Here, we report how Blissoxenos esakii (Strepsiptera: Corioxenidae) emerges from this covered site. Blissoxenos esakii was collected from nine locations in Tsukuba City, Japan, and reared in the laboratory until male emergence. Ten males successfully emerged from their hosts, and emergence was observed in four cases, including one case in which a host was parasitized by two male B. esakii . In all four cases, hosts raised their wings during male emergence, a behavior not observed in unparasitized hosts, thereby enabling B. esakii to emerge. Further investigation is needed considering the possibility that this behavior constitutes host manipulation and a common action among the hosts parasitized by corioxenids, which emergence site is covered by the host's wings.

Parasitoid wasps serve as natural enemies of numerous insect species; therefore, knowledge of host-parasitoid interactions is fundamental for understanding ecosystems. Each endoparasitoid wasp taxon exhibits a specific host range. Female parasitoids, however, occasionally oviposit into non-host species. Since the survival probability of eggs in non-host species is virtually zero, these behaviors have long been considered maladaptive. However, in the present study, we found that eggs of a specialist parasitoid, Cotesia kariyai (Hymenoptera: Braconidae), oviposited in unsuitable host caterpillars, Mythimna loreyi (Lepidoptera: Noctuidae), successfully complete larval development in the non-host when these caterpillars are simultaneously oviposited by another naturally sympatric parasitoid wasp, Meteorus pulchricornis (Hymenoptera: Braconidae), for which My. loreyi is the usual host. This observation suggests that the seemingly maladaptive behavior of ovipositing in unsuitable host insects can be adaptive, allowing them to maintain reproductive potential in environments where their ordinary hosts are absent. We propose a new term, “pirate parasitism”, for this type of obligatory multiparasitism. Understanding detailed mechanisms of this phenomenon may provide deeper insights into parasitoid-host dynamics and evolution of host use strategies by parasitoids.

Parasitoid wasps locate their hosts by tracking host‐related chemicals, such as herbivore‐induced plant volatiles (HIPVs). Attractiveness of HIPVs to parasitoid wasps has often been investigated using four‐arm olfactometers, but suitability of observation times for behavioral tests using olfactometers has received insufficient attention. In this study, we evaluated differences in results of two‐choice bioassays with multiple observation times in a four‐arm olfactometer. We found that odor preferences of the parasitoid Cotesia kariyai (Watanabe) (Hymenoptera: Braconidae) to host‐induced plant volatiles changed with time in a four‐arm olfactometer. These changes were detected only between 60–120 s from the start of experiments, and there were no changes in preference after 120 s. The gradual decrease in odor preference can be explained by habituation. It is necessary to consider habituation of parasitoid wasps to plant volatiles and to determine suitable observation times depending on the species, so that appropriate behavioral assays can be performed in a multi‐arm olfactometer or other equipment.

For many hymenopteran insects, floral pollen is essential for survival and development. Nutritional analysis of floral pollen is important to understand plant–pollinator interactions. Here, we evaluated a simple method for measuring proteins and amino acids in pollen; it requires samples far smaller than are required by conventional methods. We used a fluorometer for quantitative analysis of protein and investigated its accuracy with small samples (0.01–2.99 mg). Quantitative and qualitative analysis of amino acids was performed by conventional HPLC methods but with smaller samples (0.05–3.0 mg). The two analyses were highly accurate with samples of ≥1.0 mg. Our method allows nutritional analysis of pollen from a wide range of flower species, including those producing only small amounts of pollen, contributing to a better understanding of the interactions between flowers and flower-visiting insects.