The underground life of

Abstract. Control of seasonal wing dimorphism in the oriental mole cricket Gryllotalpa orientalis Brumeister (1839) from a wetland habitat in western Japan is described. The long-winged (LW) morph appeared from mid-June to September, whereas the shortwinged (SW) morph appeared from September to mid-June. Individuals overwintered in either the adult or juvenile stage. The seasonal shift in wing morphology was linked to the overwintering stage. Individuals that hatched in May became SW adults in September-October and then overwintered, whereas those that hatched in June and July overwintered as juveniles and became LW adults in June of the following year. The life cycle of both morphs was univoltine. Reproductive benefits and constraints of each wing morph of G. orientalis are compared.

SummarySeasonal foraging habitats, prey species and foraging frequency of Japanese Crested Ibis Nipponia nippon in farmland were studied one year after its reintroduction on Sado Island, Japan. Paddies were the main foraging habitat in spring, early summer, autumn and winter. In late summer, ibises often used levees around paddies, grasslands, uncropped paddies and abandoned paddies. Small invertebrates were important prey components in terms of frequency (70–90%) throughout the year. Ibises took Misgurnus loaches (less than 20% of prey captured) throughout the year; the capture rate of loaches in ditches was especially high in winter. Ibises depended on terrestrial invertebrates, including earthworms, particularly in late summer. No clear correlations between the rate of capture for each prey species and the proportion of habitat use in each season were detected. However, abandoned and uncropped paddies provided suitable habitats for the ibis because human disturbance was relatively low and the rate of capture for each prey type was relatively high throughout the year. Management of grass height in grasslands and on levees around the paddies will be effective in ensuring the availability of foraging habitats in late summer. Seasonal changes in the availability of foraging habitats in farmland ecosystems should be considered when designing effective management strategies for the establishment of Japanese Crested Ibis populations.

Food acquisition in animals that construct burrows for foraging is influenced by burrow structure associated with food distribution and searching patterns. The burrowing patterns of the oriental mole cricket ( Gryllotalpa orientalis Brumeister, 1838) (Orthoptera: Gryllotalpidae) were investigated based on analyses of the relation between burrow morphology and plant distribution. To assess differences between horizontal burrows (HB) with and without vertical burrows (VB), the number of branching points, the length of the horizontal parts, the plant ratio of the burrow area, and the burrow fractal dimension were compared. The size of the burrow area was positively related to the degree of branching. Cyperaceae and Gramineae occurred less frequently, whereas Hydrocotyle sibthorpioide Lam. and areas with no plants were more frequent in the burrow area than in the quadrat area. Juncaceae and Persicaria thunbergii (Siebold and Zucc.) H. Gross ex Nakai occurred more frequently and Lindernia crustacea (L.) F. Muell. occurred less frequently in HB without VB than in HB with VB. The ratio of burrow length to the number of branching points was not significantly different between HB with or without VB. HB with VB had a nearly planar structure (higher burrow fractal dimension) than that of HB alone. HB structure and plant composition of the burrow area differed depending on the presence of VB.

The oriental mole cricket Gryllotalpa orientalis exhibits variation in wing dimorphism. In an Okinawa population, no short-winged individuals were observed, and wing dimorphism has not been detected. Flight behavior of G. orientalis was observed from April to October in Okinawa. In contrast, a Hyogo population exhibited seasonal wing dimorphism and long-winged individuals appear from June to September. The flight period of the long-winged morph coincided with this period. Short-winged individuals appeared from September to the following June and they never fly. Both populations showed univoltine life cycles. Considering the possible flight period, wing pattern and life cycle of mole crickets in these two areas, it is presumed that flightlessness is expected to arise when adults can not experience suitable temperatures for flight activity.