The lygaeid bug, Dimorphopterus japonicus, is a common species in Japan which feeds mainly on the eulalia, Miscanthus sinensis. It shows a marked wing dimorphism of brachyptery and macroptery. Almost all species of the Heteroptera pass through five nymphal stadia, although some exceptions have been noted. In the present study, we observed that D. japonicus had four nymphal stadia before eclosion to adults, while Dimorphopterus pallipes, a closely related species, had five. The number of stadia in D. japonicus did not vary irrespective of sex or wing morph in our observation. This is the first report of a four stadia life cycle in lygaeid bugs. In addition, phytophagous species having a four stadia life cycle are uncommon in the Heteroptera. Although the reasons why D. japonicus has only four nymphal stadia remain unknown, it may have evolved from an ancestral species with a five stadia life cycle like D. pallipes.

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The cold hardiness of three aphid species, Acyrthosiphon pisum, Aulacorthum solani and Megoura crassicauda, was investigated using the active stages of holocyclic and anholocyclic clones. Although a progressive increase of supercooling points (SCPs) was exhibited with increasing age in the three aphid species, little variation in the SCPs was observed among the species at the same developmental stages. However, the survival rate at a prefreeze temperature of −10°C differed among the three aphid species. The survival rate of both nymphs and adults of M. crassicauda was the lowest and that of A. pisum the highest. At −10°C, the survival rate of fourth-stadium nymphs of A. pisum reared at 15°C under a short photoperiod (10L : 14D) was higher than that of the same stadium nymphs reared at 20°C under a long photoperiod (16L : 8D), but there was no significant difference in the survival rate between the holocyclic and anholocyclic clones reared under the same conditions. These results indicate that nymphs and adults of both holocyclic and anholocyclic clones have insufficient cold hardiness to survive the severe winter in the northern parts of Japan. Furthermore, the distribution of the two life cycle clones of M. crassicauda in Japan was estimated from the different levels of cold hardiness among the three aphid species.

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Abundance of live, dead and parasitized larvae of the peach leafminer, Lyonetia clerkella (Linnaeus), was investigated at 2 or 3-day intervals from April to November 1994 and April to October 1995. The proportions of infested leaves were determined by a binomial sampling in peach orchards under different management intensities, and subsequently the infested leaves were sampled to ascertain the fate of each leafminer through individual rearing in the laboratory. The seasonal prevalence showed seven discrete generations in both years. The number of larvae entering each generation was estimated by a stage-frequency analysis. From that estimate, as well as from an estimate of the number of parasitized larvae, the generational percent parasitism was determined for each generation and throughout the year. The yearly result was about 9% parasitism in the insecticide-sprayed orchards and about 19% in the unsprayed orchards. The relationship between host and parasitoid densities in successive generations showed a tendency toward counterclockwise rotation. Furthermore, the relationship between host density and percent parasitism exhibited a delayed density-dependent process in a host-parasitoid system.

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The unusual life history of bagworms, Metisa plana (Lepidoptera: Psychidae), with females completing all reproductive activity within a bag they construct as larvae, makes them ideal subjects to quantify intraspecific variations of reproductive success. This study investigated the relationship between body size and reproductive output of females, and tested the hypothesis that size-dependent variations of fecundity affect inter-generational variations of population density. Body size attained by female larvae at pupation (assessed by measuring the length of the pupal bag) was positively correlated with several parameters of reproductive output, including weight of pupae, weight and potential fecundity of calling female, as well as weight and realized fecundity of mated females. Our results further suggest that females allocate about two thirds of the resources they accumulate as larvae into egg production, and that a significant proportion of eggs are cannibalized by sibling neonates. In cage experiments, density of larvae in offspring generations on individual nursery palms was not affected by the size of females in parental generations. This result suggests that body size of females may not affect inter-generational variations of population density when potential resource depletion of host plants promotes a high incidence of dispersal among neonates.

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The use of Bacillus sphaericus (Bs) as a potential biolarvicide in India is limited due to development of resistance by the target mosquito species. Observations on the biological processes of development and resistance in the Bs susceptible population of Culex quinquefasciatus have provided good insight towards developing a better control strategy for vector mosquitoes. In a laboratory evaluation, C. quinquefasciatus susceptible to Bs attained a high resistance level (70 and 90.5 fold) at LC₅₀ and LC₉₅ levels, with several important underlying factors involving binding of Bs toxic molecules to the receptor proteins at the site of action. The resistant larvae showed insignificant variation from susceptible larvae in biological features, especially pre-oviposition period, number of egg rafts laid, incubation period, hatching percentage, stadial period, adult longevity and mortality rate. However, in vitro binding assays showed a significant reduction in the affinity of Bs toxin for the membrane receptors in the resistant strain compared to the susceptible strain.

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The trapping efficacy of a commercially available funnel-vane trap (FV trap) was compared with those of a funnel trap (F trap), a water pan trap (W trap) and a water pan trap with a vane (WV trap), baited with synthetic sex pheromone of sugarcane wireworms, Melanotus sakishimensis Ohira or M. okinawensis Ohira (Coleoptera: Elateridae) on Miyako and Okinawa Islands, respectively, in 2000. On Miyako Island, on calm days, FV and WV traps captured significantly more M. sakishimensis males than F and W traps. On windy days, FV and WV traps captured more males than F and W traps, but the differences were not significant. At Itoman on Okinawa Island, on windy days, FV and WV traps captured significantly more M. okinawensis males than F traps. On calm days, FV and WV traps captured more males than F and W traps, but the differences were not significant. In FV traps, the influence of trap height on capture was investigated in sugarcane fields on Miyako and Okinawa Islands in 2000. Traps at ground level (2 cm) and 30 cm captured more males than traps at 90 cm and 150 cm above the ground.

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Some primers occasionally fail to amplify Wolbachia DNA by a standard PCR from spider mites. In cross experiments, it is often necessary to detect Wolbachia from single individuals. Thus, six pairs of PCR primers were evaluated for their sensitivity in detecting Wolbachia in three spider mites, Panonychus mori Yokoyama, Oligonychus gotohi Ehara and Tetranychus kanzawai Kishida. Pure 100% infected populations of these three spider mites were prepared, and female adults from the infected lines at day five were examined for Wolbachia detection using the following PCR primer pairs: wsp, 16S, ftsZ(Bf-Br), ftsZ(f1-r1), ftsZ(Adf-Adr) and ftsZ(Z1-Z2). The wsp primer pair was the most sensitive: it detected the Wolbachia even from a 1/1, 000 DNA solution of P. mori with a 47.0% success rate. The 16S primer pair was the second most sensitive. The primer pair ftsZ(Bf-Br) was less sensitive. They were followed by ftsZ(Z1-Z2) and ftsZ(f1-r1) in sensitivity. Thus, the wsp and 16S primer pairs are most suitable for detecting Wolbachia in spider mites, and it is desirable to use these two primer pairs simultaneously for amplifying Wolbachia DNA from single individuals.

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Field experiments were conducted in order to evaluate the effect of trap design, pheromone quantity and trapping location on the capture of Pectinophora gossypiella in two cotton fields located in Central Greece. In the first field, three commercially available gossyplure-baited trap types were compared: two adhesive, Delta and Pherocon II, and the Funnel trap, on which moths are captured with the addition of a killing agent (DDVP strip). In the second field, Delta traps with 1, 2, 3 or 4 gossyplure lures were compared. Significant differences were noted among trap types. The Funnel traps caught approx. 4.2 and 29.9 times more moths compared to the Delta and the Pherocon II traps, respectively. The correlation of captures among the three trap types was positive and significant only until mid-July. On the other hand, throughout the entire trapping period (June–September), this correlation was significant only between the two adhesive trap types. No significant differences were noted among traps with different pheromone quantity. In addition, the correlation of captures among traps with different lure numbers was positive and significant during the entire trapping period. For both experimental fields, no significant differences were recorded between centrally located and peripheral traps, although a wider range of captures was recorded in the peripheral traps.

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Nikkomycin Z, an antibiotic, promoted infection of Bombyx mori nucleopolyhedrovirus (BmNPV) in 4th-stadium B. mori larvae, when the chemical was incorporated into the larval diet. The median lethal dose (LD₅₀) of BmNPV was decreased as the concentration of nikkomycin Z was increased. LD₅₀ of BmNPV in larvae that received 10 ppm nikkomycin Z was 0.7–1.1 polyhedra/larva. The peritrophic membrane was not observed in the gut of larvae that had received 10 ppm nikkomycin Z. Although the growth of larvae that had received 10 ppm nikkomycin Z was delayed, they molted to the next stadium.

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To establish diagnostic DNA markers useful for discriminating economically important Tetranychus species, especially T. kanzawai, from other species of the urticae complex, we sequenced the ribosomal ITS region, including ITS1, 5.8S, and ITS2, of four Tetranychus species and analyzed recognition sites of restriction endonucleases. We established genetic criteria for discriminating T. kanzawai, T. urticae, T. pueraricola and T. ludeni using PCR-RFLP. We propose the establishment of a worldwide PCR-RFLP catalogue.

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The bisacylhydrazine derivative RH-2485, which acts on certain insects as a potent ecdysteroid agonist, was injected into gregarious adult females of Schistocerca gregaria (Forskål) (Orthoptera: Acrididae). Injection of RH-2485 accelerated oviposition without affecting fecundity and life span. The first and second egg pods were laid earlier and contained more than the usual number of eggs. In subsequent egg-laying, the number of eggs per pod decreased to the control level. The weight of eggs was not affected by the treatment. All eggs laid by control females, and the eggs laid early by the treated females, contained in average 140–180 ng 20-hydroxyecdysone equivalents per egg. Ecdysteroid content, however, was nearly twice as high in the eggs from aged treated females, and this was associated with reduced hatchability. The results indicate that RH-2485 mimics the vitellogenic action of hemolymph ecdysteroids and that there may be a correlation between the level of egg ecdysteroids and the viability of embryos.

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The egg production and development of Amphibolus venator (Klug) were investigated at five temperatures (25, 27.5, 30, 32.5 and 35°C), 70% r.h. and 16L–8D photoregime. The optimum temperature for multiplication and development of A. venator was around 32.5°C. Pre-oviposition period decreased with increasing temperature. Temperature in the range 25–35°C had no effect on oviposition period. The average numbers of egg laid per ovipositing female increased with increasing temperatures, however differences were not significant. The percentages of ovipositing females at 32.5 and 35°C were the same (95.8%), but higher than in other temperatures. Total oviposition number was highest at 35°C. Egg incubation period decreased with increasing temperature, however, hatchability was not affected. The development period of nymphs decreased with increasing temperature. The lower developmental thresholds and total effective temperatures were calculated as 16.9°C and 126.6 degree-days for eggs, respectively. The corresponding values for nymphs were 20.7°C and 714.3 degree-days.

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The optimum temperature and humidity for the indoor-rearing of Bombus ignitus were investigated. The experimental regimes of temperature and humidity were defined as 23°C, 27°C and 30°C under a constant humidity of 65% R.H., and 50%, 65% and 80% R.H. under a constant temperature of 27°C, respectively. Among the temperature regimes, 27°C-rearing showed the best results, i.e., the rates of colony initiation, colony foundation and progeny-queen production at 27°C were 83%, 63% and 46%, respectively, which corresponded to 2.2–5.5 times the respective values at other temperature regimes. The numbers of progeny produced at 27°C-rearing, 164±33 workers, 553±174 males and 33±48 queens were also higher, corresponding to 21.8 and 1.5 times those at 23°C and 30°C, respectively. In terms of humidity, 65% R.H. was favorable for big colony formation. Under the same humidity, the rates of colony initiation, colony foundation and progeny-queen production were 85%, 70% and 50%, respectively, and the number of progenies reached 180±30 workers, 578±179 males and 35±38 queens. Therefore, 27°C and 65% R.H. were determined to be the favorable environmental conditions for colony development of B. ignitus in indoor rearing.

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Female adults and their offspring of tetranychid mites, Tetranychus kanzawai and T. urticae, live together on the same leaf. To clarify whether the presence of female adults affects the performance of offspring (maternal effect), we examined the performance index (fecundity after maturation) of juveniles that had lived with female adults, or without them. In either species, the presence of female adults reduced the performance index of juveniles. The effect of T. kanzawai was more conspicuous than that of T. urticae. On the other hand, female adults of T. kanzawai dispersed from an infested leaf earlier than those of T. urticae. The correlation between the maternal effect and dispersal capacity of T. kanzawai and T. urticae was discussed.

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We examined the phase variation in Tetranychus kanzawai Kishida with regard to density effects and dispersal capacity. The fecundity of females was reduced when they had lived together with senior female adults during the juvenile period was reduced. This negative density effect was not attributed to direct interference by the senior female adults, but to local alternation of the food resource caused by their feeding damage. Moreover, offspring that had developed with the female adults had a higher dispersal capacity than those that developed without female adults. This physiological and behavioral plasticity in response to local density can be considered as a kind of phase variation.

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A PCR-RFLP based method of species identification was considered for 18 pest species of Bactrocera fruit flies mainly distributed in the Asia-Pacific region. A 1.6 kb portion of the mitochondrial DNA containing portions of 16S and 12S ribosomal RNA genes was determined for eight species for which the mtDNA sequences have not been studied. Comparisons of restriction patterns expected from the sequences obtained in this and previous studies revealed that all 18 species can be discriminated by PCR-RFLP using a small number of restriction enzymes. Based on the highly conserved sequences detected among the 18 species, four sets of PCR primers were designed to amplify shorter, diagnostically informative sections within the mtDNA fragment. Given the simplicity of banding patterns and the ease of amplification of DNA fragments, such sections were considered suitable for PCR-RFLP analysis. Based on the results, a scheme for the Bactrocera pest species identification was proposed. The PCR-RFLP analysis using 83 individuals revealed that the scheme correctly identified most of the 18 species except for two closely related sympatric species, Bactrocera carambolae and B. papayae; the majority of individuals of the former species showed the same banding patterns as the latter species. In addition, molecular phylogenetic analyses were performed based on the nucleotide sequences in order to examine the positioning of each species among many other species of fruit flies.

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A cell line (BCIRL-Lepd-SL1) was established from pupal tissue of the Colorado potato beetle, Leptinotarsa decemlineata (Coleoptera: Chrysomelidae). The cell line has been in culture for three years in EX-Cell 401^TM medium supplemented with 10% fetal bovine serum, during which time it has undergone over 100 subcultures. The cell population is heterogenous in nature, consisting of round cells, trapezoid-like cells and elongated cells. The cell population doubling times at 28°C were estimated to be 3.4 days at passage 56 and 2.3 days at passage 111. The cell line did not support replication of Autographa californica nucleopolyhedrovirus (AcMNPV) recombinants carrying the genes for green or blue fluorescent proteins. The cell line was confirmed to have originated from the Colorado potato beetle by the DAF-PCR technique.

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Platypus quercivorus (Murayama) has a complicated mating behavior similar to that of other species in Platypodidae. We observed this mating behavior in the field with a video camera, and divided the behaviors into nine phases. In successful matings, three phases required a relatively long time. As the female or the male might use the three long phases for mate choice, we compared the behavior during these phases in successful matings with that in unsuccessful matings. Five of 6 females in unsuccessful matings left the gallery in the log during the phase from the entered female's emergence until the emergence of the male's elytra. The duration of this phase correlated to times that the female walked forward and backward at the entry hole during this phase, and varied much in unsuccessful matings. These results show that the female who left early in this phase may have already decided to leave during the previous phase that was from the female's first entry into the gallery until the emergence. In contrast, the female left after the extremely long duration of this phase may have been willing to select the male but disliked by the male. Thus, both male's and female's mate choice may have occurred during these continuous 2 phases.

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The insecticidal activities of compounds derived from the rhizomes of Acorus gramineus against four agricultural insect pests were examined using direct contact application method. The biologically active constituents of A. gramineus rhizomes were characterized as the phenylpropenes, cis- and trans-asarones by spectroscopic analyses. Potencies varied according to insect species, compound, and dose. In a test with female adults of Nilaparvata lugens, cis-asarone caused 100, 83, and 40% mortality at 1, 000, 500, and 250 ppm, respectively, whereas 67% mortality was achieved at 1, 000 ppm of trans-asarone. Against 3rd instar larvae of Plutella xylostella, cis-asarone gave 83 and 50% mortality at 1, 000 and 500 ppm, respectively, whereas trans-asarone at 1, 000 ppm showed 30% mortality. Against female adults of Myzus persicae and 3rd instar larvae of Spodoptera litura, cis- and trans-asarones both were almost ineffective at 2, 000 ppm. The A. gramineus rhizome-derived materials merit further study as potential insect-control agents or as lead compounds against N. lugens and P. xylostella.

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To assess the possibility of using Wollastoniella rotunda as a biological-control agent against Thrips palmi in greenhouses in Japan, the effect of temperature on development and survival of W. rotunda was investigated. Developmental times and survival rates of W. rotunda eggs and nymphs when reared on T. palmi were measured at eight constant temperatures: 15.0, 17.5, 20.0, 22.5, 25.0, 27.5, 30.0 and 32.5°C. At these temperatures, the developmental times of W. rotunda eggs and nymphs ranged from 6.6 to 29.9 days and 14.0 to 47.6 days, respectively. The developmental zero (T₀) and the thermal constant (K) were calculated to be 11.5°C and 106.4 degree-days for eggs, 9.6°C and 257.7 degree-days for male nymphs, and 9.2°C and 268.8 degree-days for female nymphs. More than 50% of the eggs died at 15.0°C and 32.5°C, while more than 70% of the eggs hatched at temperatures from 17.5 to 30.0°C. Nymphal survival rates reached 70% or more for all the temperatures tested. These results suggest that W. rotunda can survive and develop in Japanese greenhouses during the winter season.

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Seasonal adaptations were studied in a partially bivoltine population of Poecilocoris lewisi that overwinters as nymphs. Under short-day conditions, the final (5th) instar nymphs entered diapause, whereas under long-day conditions they emerged as adults within 2 weeks. The critical daylength for induction of the nymphal diapause was between 14 and 15 h at 25°C in the Osaka population. P. lewisi entered diapause in the adult stage also, under long-day conditions. Adults emerging in late spring started oviposition only after July. Insects transferred from long-day to short-day conditions at adult emergence began to lay eggs earlier and more synchronously than those kept continuously under long-day conditions due to prevention of the adult diapause. The critical daylength for induction of the adult diapause was also between 14 and 15 h at 25°C, as in the induction of nymphal diapause. The dogwood Cornus controversa, a principal host plant of P. lewisi, did not develop seeds until early July. Therefore, this suggests the absence of host plant seeds in late spring is the ultimate factor for the evolution of adult diapause in P. lewisi.

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A total of 307 soil samples, collected from two groups of Japanese oceanic islands (Daito-shoto and Ogasawara-shoto) were examined for the natural occurrence of Bacillus thuringiensis. B. thuringiensis was found in 15.3% of the soil samples, with 1.3% of the colonies belonging to the Bacillus cereus/B. thuringiensis group. Soils of the islands yielded at least 21 H serotypes. Insecticidal activities against Bombyx mori and/or Aedes aegypti were associated with 8.5% of the B. thuringiensis isolates. Among the insecticidal isolates, those belonging to the serotype H25 (serovar coreanensis) occurred predominantly.

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Vespa ducalis is a monogynous hornet with an annual life cycle. Its colonies are the smallest in the genus Vespa. Generally, it is thought that the number of queen matings and colony size are positively correlated, so we analyzed the queen mating number and genetic relatedness between workers of V. ducalis using microsatellite DNA markers. We examined foundress queens and 20 workers from each of 20 colonies. All colonies were found to have one queen inseminated by one male. The genetic relatedness between workers was 0.724±0.0029 (mean±SE), which is not significantly different from the expected value of 0.75 for full sisters. This result suggests a possible conflict in male production between queens and workers based on kin selection prediction. Therefore, we performed microsatellite analysis of 400 males from 20 colonies to verify whether males are derived from either queens or from workers. No males could be assigned to workers developed ovaries were not found in a total of 880 mature workers. These results strongly suggest that queens dominate production of males in V. ducalis colonies.

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A serious citrus pest, the ash whitefly, Siphoninus phillyreae Haliday, was first recorded in Honshu and Kyushu, Japan. The favored host plant is pomegranate (Punica granatum L.) from early summer to autumn. The adults migrate to a hedge plant (Photinia glabra (Thumb.) Maxim.) or rarely to a citrus plant (Citrus natsudaidai Hayata) before pomegranates shed their leaves in winter. Another citrus pest, the woolly whitefly, Aleurothrixus floccosus Maskell, was found from Nansei Islands to north of Tokunoshima Is., Japan. The distribution of these two pests and diagnostic features were detailed. Substrate-borne vibratory sounds produced during mating were elucidated, including new findings of male and female communication by reciprocal sound signals. It is suggested that the species-specific bioacoustic signals preserve useful information for the whitefly biosystematics of economic importance.

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Mature larvae of the flesh fly, Boettcherisca peregrina, ligated at the tenth abdominal segment in the last larval stage showed a disturbance of puparium formation (pupariation) in the anterior portion. The anterior portion of the larval body was injected with samples tested. The disturbance of pupariation in the anterior portion was dose-dependently rescued by a single injection of ecdysteroids. The minimum effective doses of exogenous ecdysteroids to induce puparial tanning at the anterior portion were 125, 64, 64, 32, 16 and 8 ng for inokosterone, ecdysone, 20-hydroxyecdysone-22acetate, ponasterone A, 20-hydroxyecdysone and polypodine B, respectively. This assay showed a similar ecdysteroid-sensitivity to a conventional bioassay but produced results approximately 2 days earlier than the conventional assay that employed the isolated abdomen of B. peregrina larvae ligated at the sixth body segment.

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