Bombyx mori ͉ enhanced locomotory response ͉ protein tyrosine phosphatase gene ͉ nucleopolyhedrovirus

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In order to elucidate the impact of secondary parasitism on a banker plant system, aphid parasitoids on banker plants were surveyed for four years in commercial greenhouses producing eggplant and sweet pepper in Kochi Prefecture, Japan. A banker plant system using Aphidius colemani was introduced into the greenhouses in November or December for the control of pest aphids from February through May. The mean rate of secondary parasitoids to total parasitoids on the alternative host aphid (Rhopalosiphum padi) on banker plants was less than 35% in the early season. In March or April, the mean rate exceeded 40%, and was more than 70% by May or June. Three main species of secondary parasitoids, Alloxysta sp. nr victrix, Dendrocerus laticeps and Syrphophagus sp., occurred throughout the season. In addition, Asaphes suspensus and Pachynouron aphidis occurred later in the season. In greenhouses where the banker plant system of aphid control failed, the increase of secondary parasitism on banker plants was sharper than in greenhouses with successful aphid control. In March and April, the higher rates of secondary parasitism on banker plants had a significant influence on the failure of aphid control.

This report assesses the primary factor for the evolution of summer diapause of the three species of sawfly, Athalia japonica, A. rosae and A. infumata that feed on cruciferous plants and coexist in the same area. A. japonica has two discrete spring and autumn generations, but A. rosae and A. infumata 5-6 generations. Only A. japonica enters summer diapause in response to the long daylengths in spring. Although these three sawflies usually feed on the same cultivated crucifers, they differ markedly in the utilization of wild crucifers. They oviposit only on young leaves. A. japonica mainly uses Gardamine plants which sprout in spring and autumn. A. rosae and A. infumata primarily use hosts with new leaves all the year round, i.e. cultivated crucifers and Rorippa indica, respectively. The thermal threshold for development is lower in A. japonica than in the other two species. The low heat tolerance of A. japonica is adapted only to cool shady habitats where Cardarnine grows. Presumably, summer diapause of A. japonica is adaptation to the deterioration of the primary host plants rather than unfavorable climatic conditions. This interpretation is supported by the movement patterns of the three Athalia sawflies, alternative means to escape from deteriorated habitat conditions. KEvwomJs: Athalia sawflies, cruciferous host plants, host plant phenology, life cycle, micro-habitat temperature, summer diapause, thermal threshold.

No abstract

SummaryThree Athalia sawflies, A. japonica, A. rosae and A. infumata, feeding on cruciferous plants, coexist in Japan. However, it is not known what ecological strategies they use and what environmental factors are crucial to such strategies. I attempted to explain these questions by examining the relationship between the spatio‐temporal distribution patterns of three Athalia sawflies and their habitats in three districts (Lowland, Intermediate and Mountain).The three sawflies have different spatio‐temporal distribution patterns, though they usually used common cruciferous plants. A. japonica was abundant in spring and autumn but disappeared during summer in all the districts. In the Lowland, populations of A. rosae and A. infumata, like that of A. japonica, crashed in summer. However A. rosae occurred mainly in summer in the Intermediate and Mountain. Although A. infumata occurred in the same seasons as A. rosae in all districts, population levels of A. infumata were always lower than those of A. rosae.The crucial factors controlling their population patterns were the availability of host plants and temperature. Population crashes of A. rosae and A. infumata were due to food depletion, and those of A. japonica were due to heat stress. On the other hand, their population patterns may be interpreted as phenological synchronization with their original host plants, though they all existed on common cruciferous plants.The three sawflies may have evolved different strategies to escape from unfavorable habitat conditions. Such strategies are speculated to be summer diapause in A. japonica, long distance migration in A. rosae, and local dispersal in A. infumata.

I compared the differences in the movement intensity of three species of sympatric Athalia sawflies, A. japonica, A. rosae and A. infumata feeding on cruciferous plants. Mark-release-recapture census was conducted to estimate movement distance, sex ratio and age composition of adult sawflies. In addition, the sex ratio of newlyemerged adults was examined by rearing field-collected larvae until adult emergence. Age composition and longevity of adults were estimated experimentally. The movement intensity was evaluated mostly with the indirect information thus obtained.Females moved more actively than males in all three sawflies. A. japonica females of all age classes moved actively in spring and autumn, but in summer they disappeared. Also, A. rosae females of all age classes moved actively in spring and autumn. In summer, in contrast with A. japonica, A. rosae females moved most actively among the three species in all seasons. A. infumata females, in particular the young females, moved most actively among the three species, except A. rosae in summer.The movement patterns of the three sawflies were deduced in relation to the spatio-temporal distributions of their habitats. In spring and autumn, when host plants were abundant, A. japonica and A. rosae females were dispersed among the host patches within the census area. In summer, however, when host plants were scarce, A. japonica entered diapause, whereas A. rosae migrated to neighboring areas. On the other hand, A. infumata, in particular young female, innately dispersed to seek for temporary host plants throughout the census seasons.

SummaryGreen larvae of the butterfly Pieris rapae and black larvae of the sawfly Athalia rosae feed on green leaves of the same cruciferous plants. To demonstrate that P. rapae has concealing coloration and that A. rosae has warning coloration, the larvae of the two species were supplied to naive chicks Gallus gallus on white, green or black backgrounds. P. rapae larvae were palatable and their green body color acted as a concealing coloration. On the other hand, A. rosae larvae were unpalatable and their black body color acted as a warning coloration.There is a general consensus that warning coloration is an altruistic character which needs victims, and thus can evolve through kin selection or green beard selection. However, black A. rosae larvae were seldom injured by chicks' attack, in particular, on the green background. Therefore, the warning coloration of A. rosae larvae can be a selfish character and hence can evolve through individual selection as well as concealing coloration of P. rapae.