The mating systems of three species of minute pirate bug,Orius sauteri,O. minutus,and O. strigicollis

We compared the mating systems and genital morphology of three Orius species dominant in Japan: Orius sauteri (Poppius), Orius minutus (L.), and Orius strigicollis (Poppius) (Heteroptera: Anthocoridae). In all three species, the males were polygamous and could inseminate at least three females at a rate of one female per day. Compared to the other two species, the O. minutus males had a lower rate of success in three consecutive mating orders. The mated females laid the same number of eggs irrespective of mating sequence. Orius minutus and O. strigicollis females were found to be monandrous, and they re‐mated with another male only when the 1st mating failed. In contrast, O. sauteri females were polyandrous and accepted a 2nd male even when the 1st mating was successful. Multiple mating with a single male did not increase their fecundity, and it decreased the hatching success of eggs. Mating with multiple males did not affect the fecundity or hatching success. Our scanning electron microscopy observation suggested that the genitalia of O. minutus and O. strigicollis were more similar in shape. The similarities in mating system and morphology between O. minutus and O. strigicollis support a close phylogenetic relationship.     

Effects of photoperiod and temperature on reproductive diapause in Ophraella communa (Coleoptera: Chrysomelidae), a potential biocontrol agent against Ambrosia artemisiifolia

Abstract To investigate the seasonal adaptation strategies of Ophraella communa to new habitats, the effects and regulation mechanisms of photoperiod and temperature on the reproductive diapause in a population collected from Changsha, Hunan were examined. Adults showed obvious reproductive diapause, which was regulated by photoperiod and temperature. At 30°C, there was no adult diapause occurring under either long‐day or short‐day conditions; at 25°C the pre‐oviposition period was short and fecundity was high in adult females under L : D 16 : 8 h, whereas under L : D 12 : 12 h, a few females entered reproductive diapause; at 20°C under short‐day conditions, all female adults entered diapause. The pre‐oviposition period was significantly prolonged when the pupae and adults were transferred from long‐days to short‐days, but the day length influence was not obvious when they were transferred only in the adult stage. However, the fecundity dropped greatly no matter whether the photoperiod shifted to short‐days only in the adult stage or whether the shift occurred in both the pupal and adult stage. The fecundity was extremely low when photoperiod shifted from long‐days to short‐days in both pupal and adult stages. This was an indication that the pupal and adult stages were the photoperiod‐sensitive stage for adult reproductive diapause. This was especially true for the photoperiod in the pupal stage, which has a distinctly significant regulative effect on reproductive diapause. Additionally, this article also addresses the reason for different photoperiodic response patterns in reproductive diapause induction between the Changsha strain and the Tsukuba strain (Japan) of O. communa.     

Induction and termination of diapause inOrius predatory bugs

Photoperiodic induction of reproductive diapause at 18°C was investigated in fourOrius [Heteroptera: Anthocoridae] species.Orius insidiosus (Say) displayed a long-day response with a critical photoperiod between L11:D13 and L12:D12. Diapause in this species was terminated rapidly when the temperature and/or the daylength were increased.Orius majusculus (Reuter) also displayed a long-day response. The critical photoperiod fell between L14:D10 and L16:D8. Diapause in this species was not terminated within 14 days when both temperature and daylength were increased. InOrius albidipennis (Reuter) no diapause could be induced at photoperiods varying from L8:D16 to L16:D8. InOrius tristicolor (White) a high proportion of diapause was found at all photoperiods tested. The effect of temperature on photoperiodic induction of diapause was studied inO. insidiosus at L10:D14. Diapause occurred at 18°C, 21°C and 25°C, but not at 30°C. Again, diapause was terminated rapidly after transfer to 25°C/L16:D8. Exposing only the nymphal instars 1–5 to short daylength was not enough to induce diapause in the whole population ofO. majusculus. Orius predatory bugs are used as biocontrol agents against western flower thrips,Frankliniella occidentalis (Pergande) [Thysanoptera: Thripidael, in greenhouses. The consequences of photoperiodic induction of diapause for the success of early season releases ofOrius are discussed.     

Light intensity and wavelength influence development, reproduction and locomotor activity in the predatory flower bug Orius sauteri (Poppius) (Hemiptera: Anthocoridae)

Light wavelength and intensity are physical factors that can affect arthropod development and reproduction. The present study examined the development, reproduction and locomotor activity of the predatory flower bug, Orius sauteri (Poppius) (Hemiptera: Anthocoridae), under five light intensities (1000, 2000, 3000, 4000 and 5000 lux) and five wavelengths [red (678.5 nm), green (620.0 nm), yellow (581.7 nm), blue (478. 1 nm) and white (all wavelengths)] at constant temperature (25 °C) and RH (70 %). The duration of nymphal development was extended at lower light intensities, primarily due to effects on the first three instars. Under white, yellow and green light, O. sauteri completed development in 18.0 days, but blue light extended development by 3.2 days and red light extended it by 7.4 days. Although lower light intensities extended the preoviposition period and reduced fecundity, they improved egg fertility. Both red and blue light negatively affected preoviposition period, fecundity and egg fertility. Whereas adult female mean walking speed over a five min period was reduced at lower light intensities, longer wavelengths (yellow and red) increased it, ostensibly reflecting an avoidance response. The respiration quotient of adult O. sauteri females was also elevated under red light conditions. These findings are informative for optimizing O. sauteri mass-rearing procedures and maximizing its efficacy as a biological control agent in greenhouse cultures.     

Effect of temperature and photoperiod on the induction of diapause in the mite Metaseiulus occidentalis

Diapause in a predaceous mite, Metaseiulus occidentalis, from a Californian vineyard population is a photoperiodically induced, facultative, adult reproductive diapause in females. The laboratory-determined critical photophase at 19°C was estimated at 11·2 hr. At 16°C, the critical photophase under laboratory conditions was approximately 11·6 hr. Temperature influenced the photoresponse of M. occidentalis so that diapause was entirely averted at temperatures of 22, 25, and 30°C. Aestival diapause at higher temperatures and long photophases was lacking. Development was continuous under constant darkness at all the temperatures tested. Diapause termination in laboratory-reared mites occurred spontaneously under the inductive conditions. Under constant 19°C temperatures, females responded to photophases so that diapause was terminated most rapidly under a 16 hr photophase (in 18·6 days); the 12 and 8 hr photophases, at this temperature, were next in their effectiveness, with 27·9 and 73·0 days, respectively, required for termination.     

Development,survival and reproduction of Orius niger (Hemiptera:Anthocoridae) under different photoperiod and temperature regimes

The successful use of the predatory bug Orius spp. (Hemiptera:Anthocoridae) for the biological control of pests, namely western flower thrips Frankliniella occidentalis (Pergande), in greenhouses during winter depends on overcoming the obstacles of short photoperiods and low temperatures which limit the efficacy of the predators through diapause induction, slowed development, reduced survival and reproduction. Thus, research has focused on determining the insect species least vulnerable to these problems. This study investigated the effect of varying day-lengths (9, 11, 13 and 16 h) at 26°C as well as constant (18, 22, 26 and 30°C) and fluctuating (10/22°C) temperatures on biological characteristics of Orius niger (Wolff). Photoperiod did not induce reproductive diapause and did not significantly affect development, survival of eggs and nymphs, longevity, fecundity or sex ratio; with the exception of the 16 h day-length which led to a shorter duration of nymphal development. Fluctuating temperatures and a constant temperature of 18°C increased the incubation period, duration of nymphal development, total developmental time, generation time and longevity, compared to the constant temperatures of 22, 26 and 30°C, but decreased fecundity compared to 22 and 26°C. On the other hand, sex ratio was not influenced by 10/22 and 18°C. Egg hatch rate and nymph survival differed significantly between temperature regimes, being lower at 18 and 10/22°C. These results suggest that O. niger would be able to survive and reproduce under winter conditions in unheated Mediterranean greenhouses and is a candidate for use in the biological control of pests.     

Identification of five Orius species in Japan by multiplex polymerase chain reaction

We developed multiplex polymerase chain reaction methods to identify five Orius (Heteroptera: Anthocoridae) species that occur commonly in Japan: Orius sauteri, Orius minutus, Orius strigicollis, Orius nagaii, and Orius tantillus. The method amplified internal transcribed spacer 1 of the nuclear ribosomal DNA by using five primers simultaneously and produced species-specific banding patterns upon agarose gel electrophoresis. Reliability of the method was tested for 350 individuals of 23 strains, and consistent results were obtained. Dichotomous keys are also provided for easy and quick species identification.     

Effects of photoperiod and temperature on diapause induction and termination in the swallowtail,Sericinus montelus

Abstract Sericinus montelus overwinters as diapausing pupae. In the present study, the effects of photoperiod and temperature on diapause induction and termination of diapause are investigated. The results obtained demonstrate that high temperature can reverse the effect of short day‐lengths on diapause induction. Under an LD 12 : 12 h photoperiod, all pupae enter diapause at 15, 20 and 25 °C, whereas all pupae develop without diapause at 35 °C. No pupae enter diapause under an LD 14 : 10 h photoperiod when the temperature is above 20 °C. Photoperiodic response curves obtained at 25 and 30 °C indicate that S. montelus is a long‐day species and the critical day‐length is approximately 13 h at 25 °C. At 25 °C, the duration of diapause is shortest when the diapausing pupae are maintained under an LD 16 : 8 h photoperiod and increases under LD 14 : 10 h and LD 12 : 12 h photoperiods. Under an LD 16 : 8 h photoperiod, the duration of diapause is shortest when the diapausing pupae are maintained at 25 °C, followed by 20 and 30 °C, and then at 15 °C. These results suggest that a moderate temperature favours diapause development under a diapause‐averting photoperiod in this species. The duration of diapause induced by an LD 12 : 12 h photoperiod is significantly longer at 25 °C than those at 15, 20 and 30 °C, and is shortest at 15 °C. At 25 °C, the duration of diapause induced by LD 6 : 18, LD 12 : 12 and LD 13 : 11 h photoperiods is similar and longer than 90 days. Thus, the diapause‐inducing conditions may affect diapause intensity and a photoperiod close to the critical day‐length has significant influence on diapause intensity in S. montelus.     

Flavonoid-producing tomato plants have a direct negative effect on the zoophytophagous biological control agent Orius sauteri

Orius sauteri (Poppius) (Hemiptera: Anthocoridae) is often used for biological control of small arthropod pests in greenhouse vegetable production systems in Asia. In addition to feeding on arthropod prey, O. sauteri consumes small quantities of plant material. Previous studies demonstrated that tomato plant chemistry confers antixenosis resistance to phloem-feeding whiteflies, but the potential nontarget effects of phytochemicals on the beneficial predator O. sauteri are unknown. Comparison of O. sauteri confined to near-isogenic lines (NILs) of tomatoes producing high levels of flavonoids (NIL-purple hypocotyl; resistant to whiteflies) and low levels of flavonoids (NIL-green hypocotyl; susceptible to whiteflies) revealed that O. sauteri had reduced oviposition, nymphal survival, and development on resistant plants, even if they were also provided with prey that did not feed on the host plant. Moreover, O. sauteri showed a significant ovipositional preference in choice assays, laying significantly more eggs on susceptible than on resistant plants. Molecular gut content analysis using the specific chloroplast trnL gene from tomato confirmed that adult and immature O. sauteri feed on both resistant and susceptible genotypes, and feeding behavior assays revealed that resistance did not affect plant feeding or prey acceptance by O. sauteri adults. These results demonstrate a direct negative effect of phytochemicals on a nontarget beneficial species and indicate that resistance mediated by phytochemicals can affect organisms that do not solely feed on phloem sap. The results also indicate that the mode of action and the potential ecological effects of phytochemical-mediated resistance are broader than previously recognized.     

Effects of photoperiod and temperature on diapause induction in Conogethes punctiferalis (Lepidoptera: Pyralidae)

The yellow peach moth, Conogethes punctiferalis (Guenée), a multivoltine species that overwinters as diapausing larvae, is one of the most serious insect pests on maize in China. Effect of photoperiod and temperature on larval diapause was examined under empirical laboratory conditions. Short‐day treatments caused larval diapause at 25°C, and the critical photoperiod was between 12 and 13 h (or 12 h 51 min) light per day. No sensitive instar was identified for diapause induction under alternated short‐ (L : D 11 : 13 h) and long‐day (L : D 14 : 10 h) treatments at different larval stages. However, accumulative treatment of three instars and 10 d under short‐day treatment was required for the induction of 50% larval diapause. All larvae entered diapause at 20°C, whereas less than 3% did so at 30°C, irrespective of the long‐ or short‐day treatment. Furthermore, under the short‐day treatment, more than 90% of larvae went into diapause with temperatures ≤ 25°C, but less than 17% did so at 28°C. In contrast, under the long‐day treatment, less than 19% of larvae went into diapause with temperatures ≥ 23°C. The forward shift (5°C) of critical temperature under the long‐day regime demonstrated the compensatory effect of temperature and photoperiod on diapause induction. In conclusion, C. punctiferalis had a temperature‐dependent type I photoperiodic diapause response; there was no sensitive instar for diapause determination, but the photoperiodic accumulation time countermeasures both of the short‐day cycles and the number of instars exposed, and the photoperiodic diapause response, was a temperature‐compensated phenomenon.     

Temperature‐dependent development of the great European spruce bark beetle Dendroctonus micans (Kug.) (Coleoptera: Curculionidae: Scolytinae) and its predator Rhizophagus grandis Gyll. (Coleoptera: Monotomidae: Rhizophaginae)

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Inheritance of photoperiodic induction of larval diapause in the Asian corn borer Ostrinia furnacalis

The Asian corn borer Ostrinia furnacalis (Guenée) enters facultative diapause as fully‐developed larvae in response to short‐day conditions. As a consequence of geographical variation in photoperiodic response, moths from Nanchang (28°46′N, 115°50′E) enter diapause in response to short day‐lengths (D strain), even at the high temperatures whereas moths from Ledong (18°47′N, 108°89′E) exhibit almost no diapause under the same conditions (N strain). In the present study, crosses between the two strains are used to evaluate the inheritance of diapause under different photoperiods at temperatures of 22, 25 and 28 °C. The moths, both reciprocal crosses and backcrosses, show a clear long‐day response, similar to that of the D strain, suggesting that the photoperiodic response controlling diapause in this moth is heritable. However, the critical day‐length for induction of diapause is shorter in hybrids than in the D strain. The N strain also shows a short‐day photoperiodic response at the lower temperature of 22 °C, indicating that the N strain still has the capacity to enter a photoperiodically‐induced diapause, depending on the rearing temperature. The incidence of diapause in all crosses is highest with D strain fathers or grandfathers and lowest with N strain fathers or grandfathers, indicating that the male parent has significantly more influence on the incidence of diapause of subsequent progeny than the female. The results obtained from all crosses under LD 12 : 12 h or LD 13 : 11 h photocycles at 25 °C show that inheritance of diapause in O. furnacalis does not fit an additive hypothesis and that the capacity for diapause is transmitted genetically in the manner of incomplete dominance.     

Acceptance and suitability of four plant substrates for rearing Orius sauteri (Hemiptera: Anthocoridae)

Orius sauteri (Poppius) is an important hemipterous predator that has been mass-reared for biological control of numerous pests in protected crop-production systems. To find a good oviposition substrate for mass-rearing this predator under insectary conditions [25°C, 65 ± 5% relative humidity, and a photoperiod of 16:8 (L:D) h], we compared kidney bean, soybean, broad bean sprouts and fresh leaves of kidney bean. We found that O. sauteri made more punctures and laid more eggs in kidney bean sprouts than in the other substrates examined. However, there were no significant differences among substrates in the proportion of punctures receiving eggs. Female O. sauteri laid the most eggs (as many as 68 eggs) in kidney bean sprouts and also had the shortest pre-oviposition period on this plant material. In addition, there were no significant differences in total oviposition durations or female longevity among the four plant substrates. The hatch rates of nymphs in the sprouts and leaves of kidney bean (>90%) were higher than those in soybean and broad bean sprouts. Thus, we found that the kidney bean sprout was the most suitable substrate for mass-rearing of O. sauteri.     

Photoperiodic Control of Pre-Adult Development and Adult Diapause Induction in Zoophytophagous Bug Dicyphus errans (Wolff) (Heteroptera,Miridae)

Zoophytophagous plant bugs (Heteroptera, Miridae) increasingly attract interest as agents of biological plant protection. In the laboratory experiment, the effects of the day length and temperature on the duration of the pre-adult period and on induction of facultative winter adult diapause were studied in Dicyphus errans (Wolff, 1804) collected in Italy. The experiment demonstrated that at 20°C the duration of the pre-adult period of D. errans significantly depended on the day length. On average, females developed 1.3 days longer than males and, at the same time, the day length equally influenced the duration of the pre-adult period in both sexes. The pre-adult period was the shortest under short-day conditions (10 to 12 h of light per day), reached its maximum at day length of 14 h, but then decreased at 15 h, and at day length of 16 h it was as short as under short-day conditions. Also, a pronounced long-day type photoperiodic response of adult diapause induction was recorded in females of D. errans at 20°C: under short-day conditions (10 to 14 h of light per day) almost all females entered diapause, whereas under long-day conditions (15 and 16 h of light per day) about 90% of females were mature. The threshold of this photoperiodic response was close to 14 h 30 min. The mean (± S.D.) egg load of mature females was 6.3 ± 4.0 eggs per female and did not depend on the day length at which the female was reared before and after the final molt. When photoperiodic response of adult diapause induction was observed at two constant temperatures (20 and 25°C), the proportion of mature females depended significantly on the day length but not on the temperature: the shapes of the photoperiodic response curves of diapause induction were almost the same within the near-threshold zone at 20 and 25°C, i.e., the photoperiodic response was thermostable. The set of two photoperiodic responses manifested at different stages of the species’ life cycle has an obvious adaptive significance. In Central Europe, D. errans has 2 or 3 generations per year and hibernates at the adult stage. Due to the thermostable photoperiodic response, females enter diapause always at the same time at the end of summer, regardless of the weather conditions of a particular year. When oviposition and pre-adult development are extended over a prolonged period in summer, nymphs from the later eggs might not be able to molt to adults in due time and then fully prepare for stable winter diapause. Under such circumstances, the photoperiodic response controlling the rates of pre-adult development acquires apparent adaptive meaning: with an autumnal shortening of the day length to 10–12 h, even under conditions of seasonal decrease in temperature, the rates of nymphal development increase and, thus, the chances of nymphs from the later eggs to molt to adults and properly prepare for overwintering also increase. The new data should be taken into account when analyzing the seasonal cycle of D. errans and developing the programs of mass rearing of this zoophytophagous mirid as an agent of biological plant protection.

     

Geographic variation in thermal and photoperiodic effects on development of zoophytophagous plant bug Nesidiocoris tenuis

The zoophytophagous plant bug Nesidiocoris tenuis (Reuter) is increasingly used for biological control of various agricultural pests. Its native range includes Southern Europe, North Africa, Southern and South‐Eastern Asia, although only the Mediterranean strains have been studied experimentally. We investigated effects of temperature and photoperiod on nymphal survival and development, rate of female maturation and egg load in two strains of N. tenuis originating from temperate and subtropical regions of South‐Eastern Asia: the ‘Temperate strain’ (from Suwon, Republic of Korea, yearly average air temperature is 13.3°C) and the ‘Subtropical strain’ (from Miyazaki, Japan, yearly average air temperature is 18.2°C). Nymphs and adults were reared on tomato leaflets and fed with eggs of the grain moth Sitotroga cerealella under four temperatures (15, 20, 25 and 30°C) and three photoperiods (10, 12 and 14 h of light per day). In spite of long‐term (40–50 generations) rearing under constant laboratory conditions, the studied strains still show a correlation between thermotolerance indices and climate at origin. In particular, at the low temperature of 15°C, survival of nymphs of the Temperate strain was double that of the Subtropical strain, whereas at the higher tested temperatures, survival of the Subtropical strain was not significantly different or even was higher than that of the Temperate strain. The duration of nymphal development in the Temperate strain was significantly shorter than that in the Subtropical strain at 15–25°C, but not at 30°C. In both strains, nymphal survival, duration of nymphal development and rate of female maturation were not significantly dependent on photoperiod, and diapause was not observed under any conditions tested. We conclude that the Subtropical strain of N. tenuis is better adapted to high temperatures, whereas the Temperate strain is more promising for application in greenhouses at medium and low temperatures.     

Diapause in the mite Metaseiulus occidentalis: Stages sensitive to photoperiodic induction

Stages of Metaseiulus occidentalis sensitive to photoperiod induction of diapause were determined by transferring various stadia into diapause-inducing conditions, and rearing them until adult females could be scored for reproductive condition. When eggs were transferred to 10 hr light at 19°C from 24 hr light at 25°C and the mites reared to adults, 92 per cent entered diapause. When larvae and all subsequent stages were kept under the inductive conditions, 62 per cent of adult females diapaused. Mites transferred as protonymphs into inductive conditions yielded only 10 per cent in diapause, and mites transferred as deutonymphs or newly emerged females did not enter diapause.However, adult females reared from eggs at 19°C under 12 hr light (which is near the critical photophase of 11·2 hr at 19°C) showed an unexpected sensitivity to photoperiod. Some newly emerged females oviposited upon transfer to an 8 hr photophase at 19°C. Some then stopped ovipositing and apparently entered diapause; these females resumed ovipositing after intervals ranging from 34 to 100 days. This was termed ‘switching’ into diapause. Some females reared under a 16 hr photophase at 19°C ‘switched’ also upon transfer as adults to shorter photophases—either 8 or 12 hr at 19°C. Thus, ‘switching’ may be due to transfer to shorter photophases. Promptness of mating vs delayed mating allowed ‘switching’ to be more easily detected.     

Interactive effects of photoperiod and temperature on diapause induction and termination in the yellow-spotted longicorn beetle, Psacothea hilaris

Abstract. The interactive effects of temperature (20 °C or 25 °C) and photoperiod (LD 12 : 12 h or LD 15 : 9 h) on diapause induction and termination are investigated in the west‐Japan type yellow‐spotted longicorn beetle, Psacothea hilaris (Pascoe) (Coleoptera: Cerambycidae). Larval diapause of P. hilaris is induced under three diapause‐inducing conditions (20 °C–SD, 20 °C–LD and 25 °C–SD), and the diapause larvae are transferred to one of four conditions (20 °C–SD, 20 °C–LD, 25 °C–SD or 25 °C–LD) for observation of pupation, which indicates termination of diapause. The intensity of diapause induced under the three conditions increases in the order 20 °C–SD < 25 °C–SD < 20 °C–LD, when assessed by the time course of pupation after the transfer. On the other hand, the effectiveness of the temperature–photoperiod combinations to terminate diapause is in the order 25 °C–SD (ineffective) < < 20 °C–LD < 25 °C–LD < 20 °C–SD. Among the temperatures (5, 10, 15 and 20 °C) examined, 15 °C is the most effective in terminating diapause under the short day; diapause in most larvae appears to have been completed in 15 days.     

Timing of diapause induction outside the natural distribution range of a species: an outdoor experiment with the bean bug Riptortus clavatus

The phytophagous bug Riptortus clavatus (Thunberg) (Heteroptera: Alydidae) produces two or three generations per year in Central Japan and overwinters in the adult stage. In bugs from the Kyoto population (35°00 N, 135°45 E), we studied (1) the effects of day-length on the nymphal and preoviposition periods under constant photoperiod at 20.5 °C, and (2) photoperiodic induction of adult diapause at 20.5 °C and under a combination of constant photoperiod and natural daily rhythm of temperature in the forest-steppe zone of Russia (50°38 N, 35°58 E). Then, we examined (3) the timing of diapause induction under quasi-natural conditions in the same region, far outside the species' natural geographical range. At 20.5 °C, the nymphal period in both males and females was significantly longer under regimes with shorter photophases than under those with longer photophases. The preoviposition period in females was significantly longer under the near-critical long-day regime L14:D10 than under typical long-day regimes (L15:D9, L16:D8, and L17:D7). The critical day-length for diapause induction was shorter under conditions of natural daily rhythm of temperature than those reported at constant 20, 25, and 30 °C. Under quasi-natural conditions in the forest-steppe zone, R. clavatus entered diapause in September, much later than the local populations of true bugs studied to date. This experiment showed that R. clavatus was maladapted to new environmental conditions: diapause was induced too late with the result that all or most nymphs hatched in late August or early September will die.     

Potential use of the fungus Beauveria bassiana against the western flower thrips Frankliniella occidentalis without reducing the effectiveness of its natural predator Orius sauteri (Hemiptera: Anthocoridae)

Orius sauteri (Poppius; Hemiptera: Anthocoridae) is an important predator of western flower thrips, Frankliniella occidentalis (Pergande; Thysanoptera: Thripidae). O. sauteri would be directly exposed to the entomopathogenic fungus Beauveria bassiana (Bals.) Vuillemin in the field should the fungus be used as a biopesticide. If the fungus were to negatively affect O. sauteri in agro-ecosystems, predation of F. occidentalis by O. sauteri may be limited. The present study was undertaken to evaluate the insecticidal activity of strain B.bassiana-RSB of B. bassiana, which is highly virulent to F. occidentalis, on the predator under laboratory conditions. Results showed that, regardless of the concentration applied to first instars, Bb-RSB was not insecticidal against O. sauteri, nor did direct applications affect the developmental rate of the predator. Significant differences in developmental rates and adult longevity were observed between O. sauteri that fed on Bb-RSB-infected F. occidentalis cadavers and those that fed on untreated thrips. Developmental time (from first instar to adult) increased from 0.3 to 0.7 days and adult longevity decreased by 0.8 to 1.2 days for predators fed thrips treated with low and high concentrations of strain Bb-RSB, respectively, compared with predators fed on untreated thrips. However, these differences were only 3–13% of mean values for the controls, suggesting that the effects of Bb-RSB on O. sauteri are relatively minor. These findings highlight the potential use of O. sauteri in combination with B. bassiana for the biocontrol of F. occidentalis, but field tests must be performed to confirm their compatible use.     

Geographic variability in diapause response of Japanese Orius species

Interspecific and latitudinal variation in diapause characteristics were examined in 12 strains of Orius species (Heteroptera: Anthocoridae) including O. sauteri (Poppius), O. nagaii Yasunaga, O. minutus (L.), O. strigicollis (Poppius), and O. tantillus (Motschulsky) from Japan. A latitudinal cline was found in the photoperiodic response controlling reproductive diapause: the lower the latitude, the lower the diapause incidence and the shorter the critical daylength. To examine the overwintering success, eight strains including four species derived from different latitudes (26–43° N) were reared outdoors in Tsukuba (36° N), central Japan from the autumn of 1998 to the summer of 1999, and their winter survival and spring fecundity were recorded. Most females of the northern strains entered diapause in the autumn when the temperature was still high, and died before winter without oviposition. In the southern strains including a nondiapause Okinawa (26° N) strain of O. strigicollis, females overwintered as well as native strains in a state of quiescence. In all strains, the winter survival was significantly lower in males than in females, and eggs and nymphs failed to overwinter.