On the main islands of Japan and in Taiwan, the spider mites Tetranychus kanzawai and T. urticae (green and red forms) are major pests on vegetable crops. The present study revealed that the dominant spider mite species injurious to vegetables in Okinawa, located between the main islands of Japan and Taiwan, differed from those in the two regions, providing important and fundamental information for controlling spider mites in Okinawa. T. okinawanus was the most dominant species throughout Okinawa with the broadest host range, even though the species has been regarded as a non-pest to date. T. piercei, which has similarly not been treated as a vegetable pest, was the second most dominant species with respect to frequency of occurrence and host range. T. kanzawai and T. urticae (green form) were comparable in the frequency of occurrence to T. piercei in the northern part of Okinawa (Okinawa Islands), whereas they were scarce in the southern part (Sakishima Islands). As other less-dominant species, T. ludeni, T. neocaledonicus and T. pueraricola were found infesting several vegetable crops. T. urticae (red form) was not found in this study.

The distribution records of Feltiella acarisuga (Vallot) (Diptera: Cecidomyiidae) in Japan were previously based only on the collecting data of Feltiella sp. from Kagoshima in 1971. We identified acarivorous gall midges collected from various localities in Japan as F. acarisuga and found that it is widely distributed in Japan from Hokkaido to Okinawa. A supplementary description to that made by Gagné in 1995 is provided, together with illustrations of the male fifth flagellomere, male genitalia, pupa, and pupal frons. We also provide information on mites on which it preys and ecological traits of F. acarisuga and devote a brief discussion to its use as a biological control agent. We newly confirm that F. acarisuga fed on Acaphylla theavagrans Kadono (Acarina: Eriophyoidea) in addition to tetranychid mites that were recorded earlier. For the convenience of applied entomologists, differences between larvae of F. acarisuga and those of other freeliving cecidomyiids that may sometimes be present on the same leaf are briefly explained.

The species composition of spider mites on crops in Okinawa is peculiar in that Tetranychus okinawanus and T. piercei are dominant on most islands, whereas T. urticae (green form) and T. kanzawai are not. To determine the source plants of Tetranychus species infesting crops, as well as to contribute to our understanding of the cause of this peculiar mite fauna, we collected Tetranychus mites on non-crop plants throughout Okinawa (more than 450 sites on 15 islands) and identified them. Except in the case of T. parakanzawai, the species frequently found on crops tended to occur frequently on non-crop plants, suggesting that the peculiar species composition on crops reflects that also on non-crop plants. T. parakanzawai has been rarely found on crops but frequently found on particular non-crop plants, possibly due to the narrower host range of this species. The type of host plants varied among mite species; for example, T. okinawanus was frequently found on indigenous plants inhabiting the seashore and invasive weeds, T. piercei and T. parakanzawai on inland indigenous plants, T. urticae (green form) on invasive weeds, and T. neocaledonicus on introduced trees. These results are of great significance when considering vegetation control as a tactic for the integrated management of spider mites.

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In general, sperm produced in the testis are moved into the seminal vesicle via the vas deferens in insects, where they are stored. How this sperm movement is controlled is less well understood in locusts or grasshoppers. In this study, the effects of age, phase variation and pheromones on male sperm storage were investigated in the desert locust, Schistocerca gregaria (Forskål). In this locust, a pair of ducts, the vasa deferentia, connect the testes to a pair of the long, slender seminal vesicles that are folded approximately thirty times, and where the sperm are stored. We found that phase variation affected the level of sperm storage in the seminal vesicle. Moreover, adult males that detected pheromones emitted by mature adult males showed enhanced sperm storage compared with males that received the pheromones emitted from nymphs: The former, adult male pheromones are known to promote sexual maturation of immature adults of both sexes, whereas the latter, nymphal pheromones delay sexual maturation. Most mature adult males had much sperm in the vasa deferentia at all times examined, suggesting daily sperm movement from the testes to the seminal vesicles via the vasa deferentia. As adult males aged, sperm were accumulated from the proximal part to the distal end of the seminal vesicle. Many sperm remained in the seminal vesicle after mating. These results suggest that young or new sperm located near the proximal part of the seminal vesicle could be used for mating, whereas old sperm not used for mating are stored in the distal part of the seminal vesicle.