Kazunori Matsuo

Two new species of Torymus Dalman, 1820 (Hymenoptera: Torymidae) parasitizing Celticecis japonica Yukawa and Tsuda, 1987 (Diptera: Cecidomyiidae) that induce leaf galls on Celtis species (Ulmaceae) in Japan

Torymus celticolus Matsuo sp. nov. and Torymus celtidigalla Matsuo sp. nov. (Hymenoptera: Torymidae) are described as parasitoids of larvae of Celticecis japonica Yukawa & Tsuda, 1987 (Diptera: Cecidomyiidae) that induce leaf galls on Celtis species (Ulmaceae) in Japan. A key to species of the genus Torymus known in Japan is provided.

An endoparasitoid avoids hyperparasitism by manipulating immobile host herbivore to modify host plant morphology.

Many parasitic organisms have an ability to manipulate their hosts to increase their own fitness. In parasitoids, behavioral changes of mobile hosts to avoid or protect against predation and hyperparasitism have been intensively studied, but host manipulation by parasitoids associated with endophytic or immobile hosts has seldom been investigated. We examined the interactions between a gall inducer Masakimyia pustulae (Diptera: Cecidomyiidae) and its parasitoids. This gall midge induces dimorphic leaf galls, thick and thin types, on Euonymus japonicus (Celastraceae). Platygaster sp. was the most common primary parasitoid of M. pustulae. In galls attacked by Platygaster sp., whole gall thickness as well as thicknesses of upper and lower gall wall was significantly larger than unparasitized galls, regardless of the gall types, in many localities. In addition, localities and tree individuals significantly affected the thickness of gall. Galls attacked by Platygaster sp. were seldom hyperparasitized in the two gall types. These results strongly suggest that Platygaster sp. manipulates the host plants development to avoid hyperparasitism by thickening galls.

Description and ecological traits of a new species of Pitydiplosis (Diptera: Cecidomyiidae) that induces leaf galls on Pueraria (Fabaceae) in East Asia, with a possible diversification scenario of intraspecific groups.

A gall midge that induces thick lenticular galls on leaflets of Pueraria species (Fabaceae) in Japan, mainland China, Taiwan and South Korea is described as Pitydiplosis puerariae sp. nov. (Diptera: Cecidomyiidae). Tanaostigmodes puerariae (Hymenoptera: Tanaostigmatidae), described earlier from mainland China as an inducer of the lenticular gall, is regarded to be an inquiline. Pitydiplosis puerariae is distinguishable from the only known congener, the Nearctic Pitydiplosis packardi, by the male genitalia with entire aedeagus and with hypoproct that is as long as cerci and bilobed with a U‐shaped emargination. DNA sequencing data indicate the existence of three genetically different intraspecific groups: (i) “YNT‐montana group” induces galls on Pueraria montana on the Yaeyama Islands, Japan and in northern Taiwan; (ii) “CT‐montana group” on P. montana in central Taiwan; (iii) and “JCK‐lobata group” on Pueraria lobata in mainland China, South Korea and Japan north of Okinoerabu Island. A possible diversification scenario of the three groups is hypothesized based on DNA sequencing data and geohistorical information. A distribution gap of the gall midge on five islands between Tokunoshima and Ishigaki Islands, Japan was confirmed by intensive field surveys. Ecological traits and adult behavior of Pity. puerariae are also described. Its possibility as a potential biological control agent against P. lobata seems counter‐indicated.

Host range of braconid species (Hymenoptera: Braconidae) that attack Asphondyliini (Diptera: Cecidomyiidae) in Japan

We reared six idiobiont braconids, Bracon asphondyliae, B. sunosei, B. tamabae, Simplicibracon curticaudis, Testudobracon longicaudis and T. pleuralis from 22 identified species and 11 unidentified segregates of Asphondyliini (Diptera: Cecidomyiidae) in Japan. A total of 22 cecidomyiid species and segregates were newly recorded as hosts of the braconids. Analysis of cytochrome oxidase subunit I (COI) did not show any evidence of host races among the braconids. Bracon sunosei, which was synonymized with B. asphondyliae, is restored to a valid species. The host range of the braconid species seemed to be related to the lineage of host genera within Asphondyliini.

Geographical and annual variations in the proportion of extended diapausing individuals of Illiciomyia yukawai (Diptera: Cecidomyiidae) with reference to an adaptive significance of its bimodal emergence pattern

Illiciomyia yukawai (Diptera: Cecidomyiidae) induces leaf galls on Illicium anisatum (Schisandraceae) and exhibits 1‐year (yr) and 2‐yr type life history patterns. Geographical and annual variations in the proportion of 2‐yr to 1‐yr type individuals of I. yukawai were studied from 1977 to 1994 and in 2008, 2009 and 2014. An analysis of geographical variation at 13 different census fields indicated that the proportion of 2‐yr type individuals significantly increased with the decrease of mean annual temperature reflected by altitudinal and latitudinal gradients. However, a multiple regression analysis indicated that the annual variation in the proportion was not correlated with temperature, gall density, abundance of host resources or parasitism by hymenopteran parasitoids. Thus, we eliminated the effects of these external factors that have been thought to determine the annual variation. We need to take alternative intrinsic factors, instead of external factors, into consideration to explain the annual variation. The fall of galled leaves occasionally caused a higher mortality of 2‐yr type individuals than those of 1‐yr type. Nevertheless, 2‐yr type individuals exist. We considered that the existence of 2‐yr type individuals of I. yukawai has an adaptive significance to diversify risks against catastrophic events such as the serious shortage of host buds and high percentage of parasitism that happen more frequently than the high mortality caused by the fall of galled leaves.

Key-factor/key-stage analysis of long-term life table data for a fruit gall midge, Asphondylia sphaera (Diptera: Cecidomyiidae)

1. Population dynamics of Asphondylia sphaera Monzen (Diptera: Cecidomyiidae), a species that induces fruit galls on Ligustrum japonicum (Oleaceae), was studied from 1970 to 1996 in broad‐leaved evergreen forests in Kagoshima, southern Japan. The numbers of fruit galls and emerging adults fluctuated greatly from year to year along with alternate year flowering of the host plant.

Life history strategy and adult and larval behavior of Macrodiplosis selenis (Diptera: Cecidomyiidae), a species that induces leaf-margin fold galls on deciduous Quercus (Fagaceae)

Life historical, behavioral and ecological traits of Macrodiplosis selenis, which induces leaf‐margin fold galls on Quercus serrata, Q. mongolica and Q. dentata (Fagaceae) in Japan and South Korea, were studied. Daily activity and larval development indicate that M. selenis is a diurnal and univoltine gall midge. In April, females lay their eggs both on upper and under surfaces of fresh leaves. The duration of the egg stage varies from 5 to 9 days, depending on daily temperatures. Hatched larvae crawl to the upper surface of the leaf margin, where they start to induce galls. Larvae become full‐grown in October, drop to the ground in November and overwinter in cocoons on the ground, while larvae of congeners mature in May and drop to the ground in June. A relatively long period of the second larval stadium from July to October on the host trees seems to be effective for M. selenis in avoiding summer mortalities caused by predation and aridity on the ground and by ectoparasitoids that attack mature larvae or pupae on the host leaves. The spatial distribution pattern of M. selenis leaf galls is contagious and the mean gall density per leaf is significantly correlated with the mean crowding. This study adds new insights of life history strategy and adult and larval behavioral pattern to the ecological knowledge of gall midges, and these kinds of information are essential for further studies of M. selenis population dynamics and interactions with other Quercus‐associated herbivores.

Description of a new and redescriptions of two known species of Torymus (Hymenoptera: Torymidae) in Taiwan with a key to Taiwanese species

Torymus flavigastris Matsuo sp. nov. (Hymenoptera: Torymidae) is described as a parasitoid of unidentified gall midges (Diptera: Cecidomyiidae) that induce galls on Litsea acuminata (Blume) Kurata (=Actinodaphne acuminata (Blume) Meisner) (Lauraceae), Machilus pseudolongifolia Hayata (Lauraceae), and Eurya chinensis Robert Brown (Theaceae) in Taiwan. This is the first record of Torymidae associated with gall midges on Lauraceae and Theaceae. Redescriptions of T. aiolomorphi and T. orientalis and a key to species of Torymus known in Taiwan are provided.

Influence of the introduced parasitoid Torymus sinensis (Hymenoptera: Torymidae) on T. koreanus and T. beneficus as indigenous parasitoids of the chestnut gall wasp Dryocosmus kuriphilus (Hymenoptera: Cynipidae) on chestnut trees in Nagano Prefecture, Japan

We describe here the parasitoid wasps Torymus sinensis Kamijo and T. beneficus Yasumatsu & Kamijo (early-spring and late-spring strains), which are introduced and indigenous natural enemies of the chestnut gall wasp Dryocosmus kuriphilus Yasumatsu, an invasive chestnut pest in Japan. We recently discovered specimens of T. koreanus Kamijo, endemic in Korea, among Torymus parasitoids collected from D. kuriphilus galls in a Japanese chestnut orchard. In this study we compare the composition of Torymus parasitoids emerging from D. kuriphilus galls before and after the release of T. sinensis. Before the release of T. sinensis, early-spring and late-spring strains of T. beneficus predominated (58.3 and 20.8% of specimens collected). However, a few years after the release, both T. beneficus strains had been almost completely displaced by T. sinensis. In contrast to the rapid decrease in T. beneficus, T. koreanus did not decrease drastically before and even after the release of T. sinensis (approximately 10–20% of specimens collected). These results suggest that not a few T. koreanus were present in the Japanese chestnut orchard investigated at least several years after the release of T. sinensis, although both the T. beneficus strains were rapidly displaced by T. sinensis during this period.

Finding of Torymus koreanus (Hymenoptera: Torymidae) attacking Dryocosmus kuriphilus (Hymenoptera: Cynipidae) in Japan.

Torymus koreanus (Hymenoptera: Torymidae) was reared from galls of Dryocosmus kuriphilus (Hymenoptera: Cynipidae) for the first time in Japan. We here report morphological features and partial mtDNA sequencing data of T. koreanus. Torymus koreanus has several common characteristics with species of the cyaneus group defined by Zavada (2003 ). According to the key to species groups defined by Graham and Gijswijt (1998 ), it does not belong to any species group because of the entire posterior margin of metasomal tergum five.