Spatial patterns formed by a small cattle herd grazing in a strip-wise pasture, which was designed to observe the cattle behavior under simple experimental conditions, were analyzed. The following problems were dealt with in this study : (1) What is the spatial pattern of a herd on the pasture, and (2) What is the spatial pattern of individuals within the herd. To the first question, the answer was that the cattle troop did not deploy in the whole area of the pasture, but formed a crowd on part of the pasture and wandered about although the troop length of cattle on the pasture fluctuated from time to time. To the second question the following two answers were given based on the analyses : (1) individuals formed a random or a slightly regular pattern within the herd when the individuals dispersed in a large area, and (2) the spatial pattern changed between aggregated, random and regular patterns within the herd when the individuals formed a crowd in a small area. Spatial pattern of individuals within the herd in the feeding phase appeared to be random, while that in the resting phase appeared to be determined by chance.

View full abstract

Females of the peacock butterfly, Inachis io geisha, oviposit their eggs on the undersurface of food plant leaves in a pyramid-shaped mass consisting of several layers. Egg masses deposited on Humulus lupulus were collected from eight sites in southern Nagano Prefecture in Japan, and the variation of egg mass size, parasitoid species and percentage parasitism of each egg mass were examined. Two species of egg parasitoiods, Telenomus sp. and Trichogramma dendrolimi, were found at all collection sites, and the percentage of parasitism of the egg masses varied from 20 to 75% depending on the collection site. The number of eggs per mass varied from ca. 40 to 800. The percentage of surface layer eggs decreased linearly with increases in egg mass size. There were upper limits in the percentage of parasitized eggs among the different egg mass sizes, although the precise relationship between egg mass size and percentage parasitism was not clear. In southern Nagano Prefecture, parasitoid utilization of I. io geisha eggs was not maximized at almost all collection site. In Minamizawa, however, almost all surface layer eggs were parasitized. At such sites, the pyramid-shape of the egg mass of I .io geisha might be expected to afford protection against parasitoid attacks.

View full abstract

Torymus (Syntomaspis) sinensis was recently recorded in South Korea as a native parasitoid of the chestnut gall wasp, Dryocosmus kuriphilus, and proved differ from a Chinese population, which was imported into Japan and has become established, in the seasonal prevalence of adult emergence. Findings of the present study suggest that the parasitoid which has been recorded in South Korea as "Torymus beneficus" is probably not beneficus but, in fact, T. (S.) sinensis, and that the Korean populations of T. (S.) sinensis might possibly consist of two types differing in the period of adult emergence. Eight species of parasitoids emerged from with-sites. Seven other parasitoids, Torymus (Torymus) geranii, Ormyrus punctiger, Eurytoma setigera, E. brunniventris, Sycophila variegata, Eupelmus urozonus and Eupelmus sp. of the first generation, were considered to parasitize the chestnut gall wasp as primary parasitoids and those of the following generations act as hyperparasitoids.

View full abstract

The sweet potato hornworm, Agrius convolvuli and the cabbage armyworm, Mamestra brassicae were reared from hatching on artificial diets supplemented with ecdysone or 20-hydroxyecdysone. The effects of the two ecdysteroids on larval development were investigated. In A. convolvuli, an extra larval molt was induced by 400 ppm ecdysone and a maximum of 4 additional larval ecdyses were induced by 800 ppm ecdysone. Conversely, 20-hydroxyecdysone did not affect larval development although much larger amounts of 20-hydroxyecdysone were present in the hemolymph than was found in the hemolymph of larvae fed ecdysone. In M brassicae, neither ecdysone nor 20-hydroxyecdysone affected larval development. Although larvae were fed on large amounts of ecdysteroids, the ecdysteroid level in the hemolymph remained as low as that in control larvae. These results suggest that ecdysone, but not 20-hydroxyecdysone, can induce multiple additional larval ecdyses in A. convolvuli, as it does in Bombyx mori, but that the sensitivities to ingested ecdysteroids differ widely among the species.

View full abstract

Feeding and reproductive activities of the leaf beetle, Pyrrhalta humeralis are suppressed during summer. The activation from this condition occurred just before October in the field. Active feeding and reproduction were induced by short day and low temperatures in the laboratory. Reproduction started at 20°C under day lengths shorter than 13.5 h, whereas 25 and 30°C inhibited reproduction even under LD 13 : 11. Reproduction was initiated at 15°C, even under LD 16 : 8, although 20 and 25°C inhibited reproduction. While 25°C failed to activate diapause females, photoperiods of 25°C and higher affected mortality. Mortality was higher under LD 13 : 11 than under LD 16 : 8. Average egg-laying was approximately 210 eggs per female at 20°C, LD 13 : 11. Photoperiodic sensitivity remained unchanged at least until mid-August and the activation can be reversed at least until mid-September.

View full abstract

Adults of a stink bug, Pyrrhocoris sibiricus, were collected from natural populations and investigated for wing length variation. The environmental factors (nymphal density, temperature and photoperiod conditions) affecting wing length variation were also investigated in the laboratory. Adults were collected in Okayama, western Japan, from July to September of 1991. To clarify the effect of nymphal density, first-instar nymphs were reared at densities of 1, 2, 4, 8 and 16 individuals per Petri dish (9 cm in diameter, 2cm in depth) under 16L-8D at 30°C. The effect of temperature was investigated by rearing first-instar nymphs at 20, 25 and 30°C under 16L-8D at a nymphal density of 8 individuals. To clarify the effect of photoperiod, first-instar nymphs were reared under 8L-16D, 12L-12D and 16L-8D at 30°C at a nymphal density of 8 individuals. The relative forewing length (RFL) and relative hindwing length (RHL) of adults collected from the field were continuously distributed in both sexes. Environmental factors such as high temperature, short day-length and moderate crowding tended to promote the production of longer hindwinged adults, although no decisive factors were determined.

View full abstract

Gronotoma hiranoi n. sp. is described and illustrated. This species is distinguishable from other members of the genus Gronotoma by the external characters of the head and mesosoma. Gronotoma adachiae BEARDSLEY, which has been recorded in Hawaii, was discovered in Indonesia, and is redescribed and illustrated. Both eucoilids are parasitic on beanflies (Diptera : Agromyzidae) including the major soybean pest, Melanagromyza sojae (ZEHNTNER) in Indonesia. Adults of the two Gronotoma species emerged from host puparia.

View full abstract

Estimation of the population density, survival and dispersal rates of the West Indian sweet potato weevil, Euscepes postfasciatus, was attempted in three areas of different vegetation with mark-recapture methods. Recapture was done by special traps baited with sweet potatoes. In a young sweet potato field, the population density and survival rate were estimated to be 576/441 m² and 0.88/10-day period by the JOLLY-SEBER method and 479/441 m² and 0.72/10-day period by JACKSON's positive method. On the other hand, in a mature sweet potato field, neither marked nor wild weevils were captured. In a study field which had recently been cleared (no vegetations), only marked insects were captured. In this field, rerecapture techniques were used to estimate the survival rate. Using the JOLLY-SEBER method and JACKSON's positive method, the estimated rates were 0.84/5-day period and 0.98/5-day period, respectively. Thus, under field conditions during winter and spring in Okinawa, both survival rate and population density of E. postfasciatus adults were high in the young sweet potato field. The results also showed that the capture rate was influenced by vegetation types. A better trapping method for mature sweet potato fields must be developed. The dispersal rate of 33 m per 5-day period in the cleared field showed high mobility of this flightless beetle under some unsuitable habitat conditions.

View full abstract

In order to establish an in vitro rearing method for an endoparasitic fly, Exorista sorbillans, various liquid media originally formulated for parasitoid rearing or for insect cell cultures were tested. About 50% of parasitoid larvae molted to the 2nd instar in the basic medium, an insect cell culture medium, MGM450, when it was fortified with 10% Bombyx mori hemolymph and 10% fetal bovine serum, whereas fewer or no larvae did so in the parasitoid rearing media formulated by other workers. Qualitative and quantitative differences were observed in hemolymph amino acids between parasitized and unparasitized 7-d-old 5th instar larvae of the host, B. mori. Heat-treated hemolymph of the host alone enabled the parasitoid larvae to develop to the pupal stage. Among the hemolymph samples taken from host larvae during the first 4 d of the 5th instar, the sample obtained from 4-d-old 5th instar larvae proved to be the best medium, and it sustained the development of larvae to the pupal stage. When such hemolymph was mixed with a modified melon fly diet or with wheat bran, some individuals of E. sorbillans completed development to the adult stage.

View full abstract

To clarify the chemical basis for the differential oviposition by two swallowtail butterflies, Papilio protenor and P. xuthus, on 4 typical host plants of Rutaceae-feeding Papilio species in Japan, Citrus unshiu, Fagara ailanthoides, Phellodendron amurense and Orixa japonica, females' responses to methanolic extracts and partitioned fractions from these plants were assayed for oviposition stimulants and deterrents. Larval survivorships on these plants were also compared as an estimate of fitness. In contrast to C. unshiu, for which both females and larvae of P. protenor and P. xuthus are successfully adapted, O. japonica was completely rejected by ovipositing females and larvae of both species. P. protenor readily accepted F. ailanthoides, but persistently avoided P. amurense for egg-laying despite its high suitability for larval growth. Unlike P. protenor, P. xuthus females only marginally accepted F. ailanthoides and P amurense were found to contain both oviposition stimulatory and inhibitory substance(s) for the two species. On the other hand, negative ovipositional responses of both species to O. japonica proved to be attributable to multiple deterrents in this plant. We conclude that differential acceptance of 4 plants by the two Papilio females can be attributed to the responsiveness of the respective species to stimulants and deterrents coexisting in the plants.

View full abstract

To determine how the spermatozoa derived from different males are used for fertilization by the multiply mated queens, the observations on their oviposition behavior and the paternity determination of their offspring by DNA fingerprinting were carried out. It was shown that sperm from different males is used unpreferentially, resulting in the co-existence of workers fathered by different males, with low average relatedness in the colony.

View full abstract

Differential cell fractionation (D.F.) and nylon wool column (N.W.) methods, both utilizing different calcium ion requirements among immunocytes for adhesion to non-self, were adopted to prepare immunocyte monolayers from Agrotis segetum and Galleria mellonella larvae. Monolayers prepared by the D.F. method were occupied predominantly by granulocytes, and those prepared by both D.F. and N.W. methods showed high purities of plasmatocytes (PL) and granular plasmatocytes (GPL). Granulocytes separated by the D.F. method in vitro showed high phagocytic activities against Indian ink particles and FITC-labeled silica beads, while PL and GPL prepared by both methods actively engulfed only FITC-labeled silica beads, similarly to granulocytes, but they could not phagocytose the Indian ink particles. Essentially similar results were obtained with monolayers from the two lepidopteran insects.

View full abstract

The blowfly, Calliphora vicina entered larval diapause after cessation of feeding in third instar under the influence of photoperiodic conditions and age of the maternal generation. Adults reared under short-day conditions (12L-12D) produced diapause-destined progeny, whereas those reared under long-day conditions (18L-6D) produced nondiapause-destined progeny at 20°C. After transfer from long-day to short-day conditions, the adults began to produce diapause-destined progeny. Even under constant long-day conditions, aged adults produced some diapause-destined progeny. Furthermore, the variation in the duration of larval development in diapause larvae was larger when the parents were old.

View full abstract

Airflow was circulated through containers with unmated females of the smoky brown cockroach, Periplaneta fuliginosa, and the sex pheromone in the vented air was absorbed on Tenax TA. Hexane extracts of the absorbed pheromone were purified and identified as periplanone-D. Periplanone-D not only elicited behavioral response in P. fuliginosa male but also elicited low activity in males of P. americana, P. japonica and Blatta orientalis.

View full abstract

Reproductive incompatibility occurred between the Sapporo (43°N) and Tsukuba (36°N) populations of the spider mite, Tetranychus quercivorus. This incompatibility was unidirectional : the Sapporo female was incompatible with the Tsukuba male, which resulted in a low egg hatchability and strongly male-biased sex ratio, whereas the reciprocal cross was comparable to intrapopulation crosses which produced normal progeny with a female-biased sex ratio. To document the geographical extent of incompatibility in local populations, these two populations were crossed with 48 local populations collected from the northern part of Japan. There appeared to be a boundary fro the incompatible area at the Shimokita Peninsula (41°N). Females from the southern populations produced female offspring when crossed with males from either Sapporo or Tsukuba, but few female offspring were obtained from crossings between females from the northern populations and males from Tsukuba. Thus, incompatibility of T. quercivorus is common and extensive among Japanese populations.

View full abstract

The synergistic effects of supernatants from cultures of nine strains of Bacillus thuringiensis toward the insecticidal activity of δ-endotoxin were investigated using neonates of the common cutworm, Spodoptera litura, and late 3rd instar larvae of the diamondback moth, Plutella xylostella by the diet incorporation method. Synergistic effects between supernatants and δ-endotoxins were detected against S. litura but not toward P. xylostella. Synergistic activity in supernatants against S. litura but not toward P. xylostella. Synergistic activity in supernatants against S. litura was observed in four strains and the occurrence was shown to be dependent on culture media. Interestingly, B. thuringiensis serovar japonensis strain Buibui and B. thuringinensis serovar morrisoni strain san diego, which produce insecticidal crystal proteins specific only to coleopteran larvae, were shown to produce synergistic factor(s) in culture supernatants. The synergistic substance(s) released into supernatants from various strains of B. thuringiensis were apparently the same.

View full abstract