Suguru Ohno

A new knotweed‐boring species of the genus Ostrinia Hübner (Lepidoptera: Crambidae) from Japan

A pyraustine species of the genus Ostrinia Hübner collected at Shigakogen, central Honshu, Japan is described as new to science under the name of Ostrinia ovalipennis sp. nov. This species is morphologically similar to the Far Eastern knotweed borer, Ostrinia latipennis, but is distinguishable from O. latipennis in wing marking and male genitalia. Larvae of O. ovalipennis feed on the knotweed, Reynoutria sachalinensis (Polygonaceae), as do larvae of O. latipennis. In Shigakogen, adults of the two knotweed‐boring species co‐occur in the same season. Adults of O. ovalipennis were captured only in July, suggesting that this species is univoltine. The fact that O. ovalipennis shares several morphological and ecological features with O. latipennis suggests that the species is the closest relative of O. latipennis.

A sex pheromone component novel to Ostrinia identified from Ostrinia latipennis (Lepidoptera: Crambidae)

Summary. Extracts from the sex pheromone gland of Ostrinia latipennis (Lepidoptera: Crambidae) were analyzed by gas chromatography-electroantennographic detection (GC-EAD) and GC-mass spectrometry. Only an EAD-active compound was detected in the extract, and it was identified as (E)-11-tetradecenol (E11-14:OH). In a wind-tunnel bioassay, E11-14:OH elicited a series of mate finding behaviors from males, although it was far less active than virgin females and crude extract of the pheromone gland. The attractiveness of E11-14:OH to O. latipennis males was confirmed by field trapping experiments. Based on these findings, we concluded that E11-14:OH, which is novel to the genus Ostrinia, is a major component of the sex pheromone in O. latipennis. The significance of the use of alcohol in place of the usual acetates in Ostrinia is discussed in relation to the pheromone biosynthesis system.

An LED-based UV-B irradiation system for tiny organisms: System description and demonstration experiment to determine the hatchability of eggs from four Tetranychus spider mite species from Okinawa.

We developed a computer-based system for controlling the photoperiod and irradiance of UV-B and white light from a 5×5 light-emitting diode (LED) matrix (100×100mm). In this system, the LED matrix was installed in each of four irradiation boxes and controlled by pulse-width modulators so that each box can independently emit UV-B and white light at irradiances of up to 1.5 and 4.0Wm(-2), respectively, or a combination of both light types. We used this system to examine the hatchabilities of the eggs of four Tetranychus spider mite species (T. urticae, T. kanzawai, T. piercei and T. okinawanus) collected from Okinawa Island under UV-B irradiation alone or simultaneous irradiation with white light for 12hd(-1) at 25°C. Although no eggs of any species hatched under the UV-B irradiation, even when the irradiance was as low as 0.02Wm(-2), the hatchabilities increased to >90% under simultaneous irradiation with 4.0Wm(-2) white light. At 0.06Wm(-2) UV-B, T. okinawanus eggs hatched (15% hatchability) under simultaneous irradiation with white light, whereas other species showed hatchabilities <1%. These results suggest that photolyases activated by white light may reduce UV-B-induced DNA damage in spider mite eggs and that the greater UV-B tolerance of T. okinawanus may explain its dominance on plants in seashore environments, which have a higher risk of exposure to reflected UV-B even on the undersurface of leaves. Our system will be useful for further examination of photophysiological responses of tiny organisms because of its ability to precisely control radiation conditions.

Female sex pheromone of Ostrinia orientalis – throwing a light on the relationship between O. orientalis and the European corn borer, O. nubilalis

Summary.The sex pheromone of Ostrinia orientalis (Lepidoptera: Crambidae) was analyzed by gas chromatography–electroantennographic detection (GC–EAD), GC–mass spectrometry and a series of bioassays. Three EAD-active compounds were detected in the female sex pheromone gland extract, and identified as tetradecyl acetate (14:OAc), (Z)-11-tetradecenyl acetate (Z11-14:OAc) and (E)-11-tetradecenyl acetate (E11-14:OAc). The titers (ratio) of 14:OAc, Z11-14:OAc and E11-14:OAc in 3-day-old virgin females were 0.49 ng (10), 4.86 ng (98) and 0.10 ng (2), respectively. In a wind-tunnel bioassay, the 98:2 blend of Z11- and E11-14:OAc, but not Z11-14:OAc alone, elicited the same male behavioral responses as virgin females and crude gland extracts. 14:OAc was inactive by itself, and did not show any synergistic effect on the binary blend. Field trapping experiments also confirmed the attractiveness of the binary blend to O. orientalis males. Based on these results, we concluded that the sex pheromone of O. orientalis is a 98:2 mixture of Z11-14:OAc and E11-14:OAc. This sex pheromone is very similar to that of the Z-type European corn borer, O. nubilalis. The present finding raises the question of whether O. orientalis , which is indistinguishable from O. nubilalis based on external morphology, is a biologically distinct species independent from O. nubilalis.

Variation in mitochondrial COII gene sequences among two species of Japanese knotweed-boring moths, Ostrinia latipennis and O. ovalipennis (Lepidoptera: Crambidae)

The Ostrinia latipennis group contains two species, O. latipennis (Warren) and O. ovalipennis Ohno. These two species commonly utilize perennial knotweeds (Fallopia spp.) as their host plants, which are serious invasive weeds in Europe and North America. Ostrinia latipennis is widely distributed across north-east Asia including Japan whereas O. ovalipennis is restricted to north Japan (Hokkaido Is.) and highland areas of central Japan (Nagano Prefecture in Honshu Is.). To estimate the phylogenetic relatedness and geographical differentiation of the two species, mitochondrial COII gene sequences were determined for specimens covering their distribution ranges in Japan. The uncorrected sequence divergence between O. latipennis and O. ovalipennis was 0.6-0.7%, supporting a close relationship. According to the standard molecular clock proposed for arthropod mtDNA, the two species are speculated to have diverged about 0.3 Myr ago. A single COII gene haplotype was found in O. latipennis irrespective of collection locality. In contrast, two haplotypes were found in O. ovalipennis, and their frequencies were significantly different between the Hokkaido and Honshu populations. The patterns of geographical variation in the COII gene within the two species were in agreement with previously reported patterns of geographical differentiation in morphology of the two species in Japan. The present results support the hypothesis that gene flow among local populations of O. ovalipennis has been limited by geographical isolation.

Wolbachia infection and an all-female trait in Ostrinia orientalis and Ostrinia zaguliaevi

Sex ratio distortion toward females (SR trait), induced by a Wolbachia bacterium, has been reported in two species of the Ostrinia furnacalis group, viz., O. furnacalis, and O. scapulalis (Lepidoptera: Crambidae). In addition, an SR trait caused by abacterial, unidentified agent(s) is known in O. scapulalis. Here we examined the SR trait in four other species of the furnacalis group, viz., O. orientalis, O. zaguliaevi, and O. zealis from Japan, and O. nubilalis from central and eastern Europe. Wolbachia infection was detected in three O. orientalis females and in one O. zaguliaevi female, and the infection was always associated with the SR trait. In terms of wsp and ftsZ gene sequences, Wolbachia strains in O. orientalis and O. zaguliaevi were indistinguishable from each other, or from those in O. furnacalis and O. scapulalis. These findings suggest that Wolbachia strains in the four Ostrinia species are probably identical. In addition, one O. zealis female, which was negative in diagnostic PCRs for Wolbachia and general bacteria, produced an all‐female brood. This trait was very similar to the SR trait caused by abacterial agent(s) in O. scapulalis.

Geographic distribution of phytoseiid mite species (Acari: Phytoseiidae) on crops in Okinawa, a subtropical area of Japan

We extensively identified phytoseiid mites co‐occurring with spider mites on crops throughout the islands of Okinawa, southwestern Japan to obtain fundamental information for controlling spider mites in the area using natural enemies. Of the 19 species found, three were new to Japan and eight were new to Okinawa. Neoseiulus womersleyi was the most common species with respect to the distribution range. Following N. womersleyi, six species including Amblyseius eharai were common, whereas N. californicus was not, suggesting that the recent change in dominant species from N. womersleyi to N. californicus observed on the main islands of Japan had not happened in Okinawa. On one small island (Tarama Island) located in the southwestern part of Okinawa, N. womersleyi was not found, and instead N. longispinosus, which is morphologically similar to N. womersleyi and has not been found in Japan, occurred. This suggests interisland differences in the relative frequencies of N. womersleyi and N. longispinosus in Okinawa.

Population dynamics of the West Indian sweetpotato weevil Euscepes postfasciatus (Fairmaire): a simulation analysis

The West Indian sweetpotato weevil Euscepes postfasciatus (Fairmaire) is a major pest of the sweet potato Ipomoea batatas (L.) Lam. and this weevil is a target of an eradication program using the Sterile Insect Technique in Okinawa Prefecture, Japan. Understanding the population ecology is essential in the planning of an eradication program; hence, a host‐plant infestation survey and light trap survey have been conducted to monitor the population dynamics of the weevil on Kume Island (Okinawa Prefecture), which is the target area of the trial weevil eradication project. Seasonal tendencies of weevil density were found in these field surveys, but the tendency found in the host‐plant infestation survey was not seen every year, and the effectiveness of the light trap is somewhat suspect. To confirm the reliability of the tendency observed in these field surveys, the present study attempted to explain the tendency by a seasonal temperature change using a temperature‐based model of weevil population dynamics. The seasonal changes of weevil density differed according to host plants and host‐plant fields. The seasonal changes of weevil density inside the host plant Ipomoea indica and outside the host plants in I. indica fields were consistent with those predicted by the model. However, those inside the host plant Ipomoea pes‐caprae in the host‐plant infestation survey were contrary to the predicted ones, and those observed outside host plants in I. pes‐caprae fields by the light trap survey were not in good agreement with the predicted ones. It was concluded that the seasonal change of the weevil density observed in I. indica and I. indica fields can be explained by a seasonal temperature change, but factors other than seasonal temperature change are needed to explain those in I. pes‐caprae and I. pes‐caprae fields.

Two mitochondrial lineages occur in the Asian corn borer, Ostrinia furnacalis (Lepidoptera: Crambidae), in Japan.

The genealogy and diversity of the mitochondrial cytochrome oxidase subunit II (COII) gene were investigated for Ostrinia furnacalis in Japan. A preliminary examination of mitochondrial lineages in China and the Philippines was also made. Two lineages (A and B) were found in the COII gene. Lineage A was frequent throughout the Japanese main islands (Hokkaido, Honshu, Shikoku and Kyushu), while the frequency of lineage B varied among these islands. No clear patterns of geographical population structure were found. Population genetic features suggested that the O. furnacalis population harboring the lineage A mitochondria expanded in the recent past, while lineage B showed weak signals of a population expansion. It is not clear whether the two lineages of mtDNA evolved in separate or identical geographical regions. We discuss two hypotheses regarding the two lineages of mtDNA: a cryptic race/species hypothesis and a selective sweep hypothesis.

Occurrence of two acarivorous species of the genus Feltiella (Diptera: Cecidomyiidae) in Okinawa, southern Japan, and redescription of F. acarivora (Zehntner)

Based on morphological features and molecular information, we record the occurrence of two acarivorous species of the genus Feltiella (Diptera: Cecidomyiidae) on some islands of Okinawa Prefecture, southern Japan. They are Feltiella acarivora (Zehntner), which is new to Japan, and Feltiella acarisuga (Vallot). F. acarivora is redescribed because the original description was incomplete. Feltiella acarivora was distinguished from F. acarisuga by having the following characteristics of male terminalia: hypoproct a little shorter than aedeagus, slightly tapering to a blunt apex with an apical ligule and gonocoxite with a hairy mediobasal lobe. For each species, we provide information on its geographic distribution, possible prey mites, and plant species on which the mites and Feltiella larvae or pupae were found. Through our surveys, we observed F. acarivora coexisting with at least eight species of tetranychid mites on various plant species, including fruit trees and vegetable crops. These observations suggest that F. acarivora and F. acarisuga contribute to the control of pest tetranychid mites in Okinawa.