Geographical variation in body size, development time, and wing dimorphism in the cricket Velarifictorus micado (Orthoptera: Gryllidae)

Abstract

We examined whether body size, development time, and wing dimorphism are affected by latitude in the cricket, Velarifictorus micado (Saussure). We found that the number of days required for nymphal development decreased with increasing latitude, suggesting that shorter periods of warm temperatures in the north resulted in faster development. Body size varied between populations, and followed the converse to Bergmann's rule, indicating that limited development time at higher latitudes resulted in smaller body size. Wing dimorphism in V. micado was influenced by both photoperiod and latitude. A higher proportion of macropters occurred under longer photoperiod conditions, suggesting that wing dimorphism in V. micado was the result of seasonal adaptation. The critical photoperiod was shorter for the southern populations than that for the northern populations, and the incidence of macroptery decreased with increasing latitude, suggesting that wing dimorphism in V. micado correlated with climatic variation.