All females of Orius sauteri exhibited reproductive diapause at 22°C but 37% of them initiated oviposition at 26°C under 10L-14D. Although less females initiated oviposition under 10L-14D than under 14L-10D at 26°C, the mean preoviposition period under 10L-14D was shorter than that under 14L-10D at 26°C. The short photoperiod did not appear to prolong the preoviposition period under 26°C. If O. sauteri is used as a biological control agent against non-diapausing thrips like Thrips palmi in greenhouses under short photoperiod, maintaining a high temperature should be considered to prevent reproductive diapause induction in O. sauteri.

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The leaf area of a solanaceous weed, Solanum carolinense, consumed by larvae and adults of a leaf scraping coccinellid beetle, Epilachna vigintioctopunctata, was measured using a computer-assisted image processing system (IPS). The accuracy of this IPS was examined by measuring areas of 25 mm×25 mm, 50 mm×50 mm, and 100 mm×100 mm reference plates. The relative measurement error of the IPS was <1% for all plates. It was also demonstrated that the IPS could be effectively used to measure the leaf area consumed by a leafscraper insect by comparing the IPS measurements with those of an area meter. A feeding experiment of E. vigintioctopunctata on S. carolinense was carried out for 38 days at 25°C under 16L-8D, and the leaf area consumed was measured by the IPS. An average beetle consumed 1, 429.5±131.6 (S. D. ) mm² of leaves to complete its larval development and consumed 2, 510.9±306.2 mm² of leaves during the first 10 days of its adult stage.

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Colonies of the brown planthopper (BPH), Nilaparvata lugens (Stal), virulent against two resistant rice cultivars carrying BPH resistance genes, either bph8 or Bph9, were selected under laboratory conditions. Two BPH resistant indica cultivars, Thai Col. 11 (a bph8 carrier) and Pokkali (a Bph9 carrier), were used as selection hosts on which the wild-type population of BPH was continuously cultured. The virulence or adaptation was monitored on the resistant hosts during the selection process based on the following five parameters ; survival rate, wing dimorphism, oviposition, egg hatch and egg hatchability. Selection appeared to be achieved at the 9th-15th generations depending on the parameters and the selection hosts. The colony selected on Thai Col. 11 showed a high level of virulence not only against the selection host but also against another bph8 carrier, cv. Thai Col. 5. The colony selected on Pokkali also showed virulence on the selection host but this virulence was unstable and not effective against another Bph9 carrier, cv. Balamawee. Our results suggested the presence of virulent BPH individuals (forerunners) in the wild population that could effectively be selected on resistant rice hosts with specific major resistance genes. The genetic system of BPH virulence and rice resistance is discussed.

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Light microscopy, chemical analysis and wind tunnel experiments were used to study the female sex pheromone gland in the European grapevine moth, Lobesia botrana. Two distinct areas of the intersegmental membrane (ISM) between the last abdominal segments VIII and IX are involved in pheromone production : the dorsal part and the ventral sac. Extracts of the dorsal part of the ISM elicited a stronger male attraction response in the wind tunnel than extracts of the ventral sac. A combination of extracts elicited a higher male response than extracts made from either part of the ISM alone. Chemical analysis indicated presence of different compounds in both parts, with the main pheromone compound, (E)-7, (Z)-9-dodecadienyl acetate (E7, Z9-12Ac) occurring only in the dorsal part of the ISM.

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An allozyme survey of 30 species of Japanese plusiine moths was made by means of polyacrylamide gel electrophoresis. Comparison of zymograms of several enzymes, and genetic identity and distance measures were calculated from allele frequencies of 4 electrophoretical loci from 3 enzymes (esterases, hexokinase and phosphoglucomutase), and then UPGMA phenograms and Wagner procedure distance phenograms of plusiine moths were made from the measures. In the phylogenetic analyses, the 30 plusiine species were divided into three groups. These three groups mainly coincided with tribes that were prescribed by previous classifications based on external morphological characters. The obtained phenograms, however, appear to suggest that Ctenoplusia albostriata and other members of the genus Ctenoplusia have separate identities, although they are related species based on morphological characters. The phenograms may also indicate that (1) there is a close association of the genus Anadevidia and the "Autographa group, " whereas their morphological characters did not support this association, and (2) the genera Diachrysia and Plusia should be separated from other genera belonging to the tribe Plusiini, although external morphological characters indicate that these two genera belong to the tribe Plusiini.

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An artificial leaf used for oviposition by the sweet potato hornworm, Agrius convolvuli (Lepidoptera, Sphingidae), was developed based on observations of adult behavior. It consists of a truncated cone disc sandwiched between a sheet of filter paper (top) and a plastic disc (bottom). The filter paper was kept moist by absorption of a leaf extract. Eggs were laid mainly on the lower surface of the plastic disc which was convenient for the collection of eggs. Oviposition behavior was well stimulated when the artificial leaf was supplied with the leaf extracts of fresh sweet potato leaves. Using a diluted ethanol extract (equivalent to 0.06 g fresh leaf/ml), 400-600 eggs/female were laid as many as when a potted plant was used. Observations using the artificial leaf revealed that the phytochemically-mediated oviposition behavior of this moth can be described as follows : 1) oviposition in both mated and unmated females is stimulated by the contact with phytochemicals of the host plant ; 2) in addition to high air humidity (>70% RH), moisture at the oviposition site is necessary to induce oviposition ; 3) egg-laying can be induced by host-plant volatiles alone although oviposition behavior is remarkably stimulated by both volatile and non-volatile compounds ; 4) chemoreceptors for the oviposition stimuli are located not only on the tarsi but also on the antennae ; 5) the tarsi are important to stimulate oviposition rather than the antennae ; however, 6) the antennae play an important role in the location of oviposition site. It can be concluded that the phytochemically-mediated oviposition sequence is accomplished through synergistic chemoreception by antennae and tarsi in A. convolvuli. Because of the high yield and the ease of egg collection, the artificial leaf is useful not only for the study of oviposition behavior, but also for successive maintenance of laboratory colonies of this insect.

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In the adult stage of the leaf beetle, Gastrophysa atrocyanea, a diapause-specific peptide appeared at diapause initiation and disappeared after overwintering. Continuous JHA applications induced the diapause breakdown which caused the peptide to decline. To isolate the peptide, we used disk preparative SDS-PAGE, gel filtration HPLC and RP-HPLC. The apparent molecular mass of the peptide was 7.9 kDa with SDS-PAGE and 4466.3 Da by mass spectrometry. The first 36 the N-terminal amino acid sequence of the peptide showed : AVRIGPXDQVXPRIVPERHEXXRAHGRSGYAYXSGG. Antiserum prepared for the peptide was used for western blotting and immunohistochemistry. The results suggested that it is synthesized in the fat body and released into the hemolymph.

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Four species of planthoppers were collected using net traps and an aspirator on a weather ship above the Pacific Ocean. An entomogenous fungus, Erynia delphacis (Entomophthorales), was isolated from a specimen of the whitebacked rice planthopper, Sogatella furcifera. The fungal isolate was infectious to 3 species of planthoppers, Sogatella furcifera, Nilaparvata lugens. Laodelphax striatellus, and the green rice leafhopper, Nephotettix cincticeps, under laboratory conditions. The results suggest that E. delphacis migrated into Japan from overseas through migratory planthoppers.

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To reveal the regulatory mechanism of G₂-arrest of cell division in embryos at the diapause stage of the silkworm, Bombyx mori, the profiles for mRNA levels of a Bombyx homologue of Cdc2 and a novel Bombyx Cdc2-related kinase (Bcdrk) were examined during ovarian development, early embryogenesis and diapause stage, using a reverse transcription/polymerase chain reaction system. Although levels of mRNAs for Cdc2 and Bcdrk were higher in paired ovaries during the early pupal stage, the levels decreased at the middle stage. Both mRNAs became abundant in oocytes towafd the maturation. From oviposition up to the stage just before cellular blastoderm, high levels of both mRNAs were maintained, and thereafter the levels declined. In diapausing eggs kept at 25°C, mRNA levels remained lower, whilst in diapause eggs exposed to 5°C from 2 days after oviposition, in order to break diapause, relatively higher levels of mRNAs were found. In eggs treated with HCl to avert the entry into diapause, mRNA levels per egg for Cdc2 and Bcdrk increased 2 days after treatment, although these increases were not observed in terms of mRNA levels per actin mRNA. These results were discussed in relation to the activities of nuclear/cellular division in ovaries and eggs. In addition, Bcdrk was suggested to play a role similar to that in Bombyx Cdc2 kinase, because the changing profile for levels of Bcdrk mRNA resembled that for cdc2 mRNA.

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In order to understand the role of traumatic resin duct formation in the inner bark as a host defense reaction to larval feeding damage, six 11-year-old Japanese cedar trees (Cryptomeria japonica) were inoculated with larvae of the cryptomeria bark borer (Semanotus japonicus). The spatial extent of this defense reaction was measured one, two, and three months after inoculation by examining the occurrence of newly formed resin ducts in more than 720 bark samples per tree. Two types of spatial extent of the responding inner bark area were observed in the experimental trees : localized and systemic. In four trees, showing the localized response, most of the induced resin ducts were confined to the proximity of each larval gallery, and the area of responding inner bark was positively correlated with the substitutive value for larval gallery length. In two other trees, showing the systemic response, induction of resin ducts was not localized but extended throughout the whole trunk.

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Partial 18S, 5.8S and the intervening internal transcribed spacer region 1 (ITS-1) of nuclear ribosomal DNA from representatives of 10 species of the genus Orius and one outgroup species (Wollastoniella rotunda Yasunaga et Miyamoto) were analyzed by PCR and DNA sequencing. Within the taxa analyzed, the length of the ITS-1 region varied from 230-663 bp. Phylogenetic trees generated from informative sites within the sequences were highly resolved in the proximal regions of the branches, but more ambiguous deeper within the tree. Orius species relationships showed some agreement with anecdotal morphological observations and this study represents a first attempt in establishing Orius species relationships.

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We studied the effect of Tetranychus urticae-infested plant volatiles on the resident time of the predatory mite Phytoseiulus persimilis on a kidney bean leaf disc with T. urticae eggs. The leaf was set in a wind tunnel into which either T. urticae-infested or -uninfested leaf volatiles were introduced. With both volatile flows, the predators showed longer resident time in discs with prey eggs than in those without eggs. At the same egg density levels per disc, the predators stayed longer in uninfested-leaf volatile flow than in infested-leaf volatile flow. Chemical analysis showed that the infested leaves produced seven terpenoids [ (3E)-4, 8-dimethyl-1, 3, 7-nonatriene, (3E, 7E)-4, 8, 12-trimethyl-1, 3, 7, 11-tridecatetraene, α-copaene, β-caryophyllene, α-humulene, germacrene-D and α-farnesene] and methyl salicylate. The results suggest that the predators utilize both the prey density level in a patch they currently inhabit and T. urticae-infested volatiles from outside the patch for determining whether to remain in or leave the patch.

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Parasitoid fauna of the serpentine leafminer Liriomyza trifolii (Burgess) was surveyed in Okinawa Is., Miyako Is. and Ishigaki Is. in southern Japan from November through December 1997. A total of 12 species of parasitoids were recorded as natural enemies of L. trifolii ; including one Braconidae, one Eucoilidae, two Pteromalidae, and eight Eulophidae (7 genera). All dominating species were members of the Eulophidae. In the field, Neochrysocharis formosa was the most dominant species among the three islands, and the second most dominant species was Hemiptarsenus varicornis in Okinawa Is., Neochrysocharis okazakii in Miyako Is. and Chrysocharis pentheus in Ishigaki Is. On the other hand, in a vinyl greenhouse, the dominant species were H. varicornis and N. formosa in Okinawa Is., and N. formosa and N. okazakii in Ishigaki Is. Sex ratios of the three main parasitoid species, H. varicornis, C. pentheus and N. okazakii, were nearly 0.5 for the three islands. However, the sex ratio of N. formosa was extremely female biased 0.996 in Okinawa Is., 0.86 in Miyako Is. and 0.97 in Ishigaki Is. These facts indicate that both sexual (arrhenotokous) and asexual (thelytokous) forms of N. formosa occur sympatrically, and the asexual strain predominated in populations of N. formosa.

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Sexual differences in the transmission and accumulation of tomato spotted wilt virus (TSWV) were investigated in adults of the western flower thrips, Frankliniella occidentalis. Both TSWV transmission rates to petunia leaf disks and the triple antibody sandwich enzyme-1inked immunosorbent assay (TAS-ELISA)-positive rates showed no significant difference between the sexes. In ELISA-positive thrips, however, males transmitted TSWV to leaf disks with a significantly higher efficiency than females : 81% in males and 47% in females. Apparently, TSWV-transmitters had higher ELISA values than non-transmitters, and the average ELISA value of female transmitters was approximately 2 times that of male transmitters. These results suggest that TSWV may have a higher propagation rate in females than in males, whereas the efficiency of the virus transmission by males may be greater than that by females if they become viruliferous adults. Potential causes for these differences are discussed.

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