Population genetics of invading pests can be informative for understanding their ecology. In this study, we investigated population genetics of the invasive alfalfa weevil Hypera postica in Fukuoka Prefecture, Japan. We analyzed mitochondrial tRNALeu-COII, nuclear EF-1α gene fragments, and Wolbachia infection in relation to three leguminous host plants: Vicia angustifolia, Vicia villosa, and a new host Astragalus sinicus cultivated as a honey source and green manure crop. A parsimony network generated from mitochondrial gene sequences uncovered two major haplotypic groups, Western and Egyptian. In contrast to reported Wolbachia infection of the Western strain in the United States, none of our analyzed individuals were infected. The absence of Wolbachia may contribute to the stable coexistence of mitochondrial strains through inter-strain reproductive compatibility. Hypera postica genetic variants for the mitochondrial and nuclear genes were associated neither with host plant species nor with two geographic regions (Hisayama and Kama) within Fukuoka. Mitochondrial haplogroups were incongruent with nuclear genetic variants. Genetic diversity at the nuclear locus was the highest for the populations feeding on V. angustifolia. The nuclear data for A. sinicus-feeding populations indicated past sudden population growth and extended Bayesian skyline plot analysis based on the mitochondrial and nuclear data showed that the growth of A. sinicus-feeding population took place within the past 1000 years. These results suggest a shorter history of A. sinicus as a host plant compared with V. angustifolia and a recent rapid growth of H. postica population using the new host A. sinicus.

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The functional response of the indigenous green lacewing Chrysoperla nipponensis (Okamoto) and the imported green lacewing Chrysoperla carnea (Stephens) (Neuroptera: Chrysopidae) feeding on seven different densities of the cotton aphid Aphis gossypii (Glover) (Homoptera: Aphididae) was studied under laboratory conditions at 20°C. C. nipponensis and C. carnea have shown a Type II functional response based on logistic regression analysis. The maximum number of prey eaten by C. carnea was higher than C. nipponensis. Handling time decreased at 24 h for both species, but was higher for C. nipponensis at 12 and 24 h than for C. carnea. The attack coefficient of C. nipponensis was slightly higher than C. carnea in second and third instars. These results indicate that C. carnea may eat more aphids at high prey densities; however, C. nipponensis could be considered a prospective candidate for use as a commercial biological control agent for aphids in Japan. C. nipponensis will become more important than C. carnea from the viewpoint of environmental safety because it is a native species adapted to the Japanese environment, and nontarget effects can be avoided.

The harmful side effects of 11 pesticides, 5 acaricides, and 10 fungicides on nymphs and adults of the predatory mirid bug Pilophorus typicus Distant (Heteroptera: Miridae) were determined by dipping them into solutions of each chemical. Two insect growth regulators (IGRs), buprofezin and cyromazine, were not harmful to nymphal survival of P. typicus on the fifth day. Flufenoxuron, lufenuron, and novaluron (also IGRs) were seriously harmful to nymphal survival of P. typicus on the fifth day. IGRs that were deleterious to nymphal survival were probably harmful because they regulated molting. Three insecticides, buprofezin, cyromazine, and pyridalyl; one acaricide, bifenazate; and four fungicides, boscalid, captan, iprodione, and triadimefon, were found to be inert pesticides for nymphs and adults of P. typicus.

The substrate-borne vibrational courtship songs of type A and type B Chrysoperla nipponensis (Okamoto) (Neuroptera: Chrysopidae) are described in detail, from populations sampled throughout Japan and near Beijing, China. The song of type A is long (≈ 5–6 s) and is made up of numerous (four to 12) volleys of four distinct forms that differ in their carrier frequencies. The song of type B is shorter (≈2 s) and functions as a repeated single-volley song, but each volley is shown here to consist of four to six distinct subsections. During heterosexual duets, partners of type A exchange their long multi-volley songs, whereas partners of type B repeatedly exchange short single-volley songs. Geographical variation within each song type is low and largely insignificant. In addition, previously recognized mitochondrial (cytochrome oxidase subunit I) haplotypes Al and A2 of type A C. nipponensis do not have different songs. These results support the hypothesis that types A and B C. nipponensis are distinct species, with type A corresponding to the nominate species (i.e., C. nipponensis s. str.) and type B as yet unnamed. Their songs are among the most complex yet found in the Chrysoperla carnea swarm of cryptic species.