Applied Entomology and Zoology

When prey encounter predators, they exhibit antipredator responses to reduce their risk of predation. Delayed responses can be fatal. Because prey can assess the risk of predation using predation-related cues, previous exposures to these cues could affect subsequent antipredator responses. We tested this possibility using the pea aphid Acyrthosiphon pisum Harris (Hemiptera: Aphididae) and its predator the Asian ladybird beetle, Harmonia axyridis Pallas (Coleoptera: Coccinellidae). Aphids disperse from their host plants after sensing predators. We investigated whether previous exposures to cues from conspecifics and ladybird beetles affected the dispersal rates of aphids encountering predators. The cues contained visual, chemical, and vibrational information from aphids and ladybird beetles. Aphids that had previously been exposed to these cues increased dispersal rates and, consequently, suffered less predation than unexposed aphids. To clarify how aphids increased their dispersal rate, we examined their feeding times. Aphids that had been exposed to cues reduced feeding times compared with unexposed conspecifics. Therefore, we further tested whether the predator-induced dispersal of non-feeding aphids was greater than that of feeding conspecifics and found correlated differences. Previous exposures to cues from conspecifics and predators may allow prey to tune their antipredator responses to predation risk prior to further predator encounters.

Hai loài mới thuộc chi Morophagoides Petersen từ các vùng Kyushu và Kanto (tỉnh Gunma và Tokyo) của Honshu, Nhật Bản, được mô tả. Chúng đã bị nhầm lẫn với M. moriutii Robinson, một loài sâu hại nghiêm trọng của nấm shiitake, Lentinula edodes (Berk.) Pegler. Các loài mới này rõ ràng có thể phân biệt không chỉ bởi bộ phận sinh dục của con đực và con cái trưởng thành mà còn bằng cách sử dụng mã DNA.

Biological observations of Paramblynotus koreanus Choi and Suh (Hymenoptera: Cynipoidea: Liopteridae) occurred on Quercus serrata Thunb. Trees suggested that their host was Carcilia strigicollis Roelofs (Coleoptera: Curculionidae). The species-specific loop-mediated isothermal amplification (LAMP) assay designed for C. strigicollis successfully detected C. strigicollis DNA in the residue of P. koreanus pupal chamber, which demonstrated that this species is a host of P. koreanus. This is the first definitive host record for the Liopteridae.

We examined the genetic variation in the sequences of cytochrome c oxidase subunit I gene (DNA barcode region) and some other regions of mitochondrial DNA of sweet potato weevil, Cylas formicarius (Fabricius, 1798) (Coleoptera: Brentidae), and West Indian sweet potato weevil, Euscepes postfasciatus (Fairmaire, 1849) (Coleoptera: Curculionidae), in Japan. In the DNA barcode region of C. formicarius, 139 haplotypes were detected from 1705 individuals belonging to 46 geographical populations. In the maximum likelihood phylogenetic tree, haplotypes found in Japan were mainly divided into three clades. In the DNA barcode region of E. postfasciatus, two haplotypes were detected from 82 individuals belonging to eight geographical populations. Of those haplotypes, Hap 1 was detected from the Nansei Islands, Fiji, Samoa, and Tonga, while Hap 2 was detected from the Nansei Islands and Samoa. These results suggest that the Japanese populations of both the species were derived from several foreign countries. Based on the haplotype network analyses of some other gene regions, those regions may be useful for a more detailed estimation of the origin of an accidentally collected individual in non-distribution area in Japan.

We examined whether the application of a powdered artificial diet on target plants would promote the establishment of Geocoris varius (Uhler) (Hemiptera: Geocoridae). Laboratory trials showed that, after 72 h, 93 % of the G. varius individuals remained on plants to which the artificial diet was applied as opposed to only 30 % of G. varius remaining on untreated strawberry plants. Moreover, application of the powdered diet promoted the development of G. varius from the third to the fifth nymphal stages and extended the average longevity by 12 days. The results suggested that the application of powdered artificial diet promotes the establishment of G. varius released in a greenhouse, even when pest densities are low, increasing the effectiveness of biological control. Furthermore, the increase in predation associated with greater numbers of more developed G. varius would improved the effectiveness of this biocontrol method.

Conogethes punctiferalis (Guénee) is a critical pest that commonly infests castor (Ricinus communis Linnaeus) and cardamom (Elettaria cardamomum Maton) in India. The moths of both castor and cardamom appear to be similar in wing pattern and color. However, the results of behavioral studies elicited a doubt that there may be differences in terms of host specialization. In the present study, we conducted morphological studies and DNA barcode analyses using cytochrome oxidase I gene, which unraveled the mystery of C. punctiferalis breeding on castor and cardamom. The differences in male aedeagus and female bursae were prominent, yet, not sufficient enough to say that they are different species. The results showed high haplotype diversity (0.817 ± 0.073) and nucleotide diversity (0.0285 ± 0.002) in C. punctiferalis. In addition, topologies of neighbor-joining trees indicate that Conogethes sp. breeding on castor belongs to C. punctiferalis while those on cardamom are of a separate clade. Further genetic analysis revealed significant genetic differentiations among the two sampled populations, reflecting limited gene flow. Neutrality tests and mismatch distributions showed population expansion in C. punctiferalis, while the results of an analysis of molecular variance (AMOVA) indicated the existence of significant genetic variation among the examined host races. Conclusively, analysis using mitochondrial DNA showed an amount of genetic divergence between the two host-associated populations compatible with cryptic species rather than host races.

In most animals, morphological changes are closely correlated to changes in behavior during ontogeny. Females of the winter cherry bug, Acanthocoris sordidus (Thunberg), often oviposit away from host plants. First-instar nymphs of A. sordidus can develop to the second instar only with water. Thus, it is the second-instar nymphs that have to search for host plants when A. sordidus females oviposit off host plants, implying that movement is of greater importance during the second instar than during other instars. We investigated the relative growth pattern of nymphal legs of A. sordidus to determine whether the morphology of this species is adapted to changes in locomotion. For comparison, we examined the relative leg lengths of the nymphs of two species, Hygia opaca (Uhler) and Leptocorisa chinensis Dallas, that do not need to search for their host plants due to the species’ oviposition habits. As predicted, second-instar nymphs of A. sordidus had the longest relative leg length of all instars. On the other hand, the relative growth patterns of the nymphal legs of H. opaca and L. chinensis differed from that of A. sordidus, indicating that relative leg growth is more strongly affected by oviposition habits than by phylesis.

Most insects must accumulate glycogen before entering diapause. Photoperiod influences diapause beyond the maternal generation in Cotesia vestalis (Haliday) (Hymenoptera: Braconidae). In this study, we measured glycogen content and the activity and messenger RNA (mRNA) expression of glycogen synthase and glycogen phosphorylase at different G0 (25 °C under light:dark photoperiods of 8L:16D, 12L:12D, and 16L:8D) and G1 life stages (13 °C under 8L:16D). Glycogen content in G0 and G1 increased with shorter light periods, except for G0 adult males, which showed no significant difference under the three photoperiods. Compared with those under 16 h, in those under 8 h light, glycogen synthase activity was significantly higher at all tested stages, except for G0 pupa and adult male, for which it was identical; mRNA expression was higher at G0 larva and prepupa, lower at pupa, and identical at rest stages. Glycogen phosphorylase activity was significantly higher for G1 egg, lower at G1 prepupa, and identical at all other stages; mRNA expression was higher at G0 and G1 larval stages, and similar at rest stages. These findings suggest that glycogen, being regulated by the two enzymes, may be a consequential factor in the transmission of maternal information and diapause induction of C. vestalis.

The abundance of the adult brown-winged green bug, Plautia stali Scott, varies annually. During outbreaks, P. stali causes severe damage to various fruit crops. Therefore, predicting its abundance beforehand is important. In this study, we constructed multiple regression models to predict the abundance of overwintered adult P. stali in Chiba Prefecture, Japan, by using the accumulated aggregation-pheromone-trap captures of P. stali and the male flower production of sugi Cryptomeria japonica (Thunb. ex L.f.) D. Don, which relates to cone production, from 1998 to 2016. The abundance of overwintered adults in the present year can be predicted by male C. japonica flower production and the abundance of P. stali adults in the previous year. The models are highly precise and can calculate estimates in August for the abundance in the next year, which is far enough in advance for the application of control measures. These models also indicate intraspecific competition for food resources in P. stali.