Wing polymorphism inNysius huttoniWhite (Hemiptera: Orsillidae)

Abstract

Individuals of Nysius huttoni White, a ground-dwelling hemipteran, develop one of three wing forms. Field studies were carried out from 1995 to 1998 to investigate the proportion of each wing form; adult populations consisted of 94.1% macropters, 5.5% sub-brachypters and 0.4% brachypters. Paired mating adults were collected for two years in 1995Á1996 and 1996Á1997 to investigate which wing forms were mating with which, and the proportions of the wing form combinations among the mating pairs. Theoretically, there are nine possible mating combinations among three wing forms. However, only six mating combinations were found in the field. Four mating combinations, M)M, àM) ßSb, ßM ) àSb and Sb)Sb occurred in both years; and two mating combinations, ßM ) àB and ßSb ) àB were found only in 1996Á1997. The other three mating combinations, àM) ßB, àSb) ßB and B)B were not found in either year. M )M was the predominant mating combination with an average percentage of 81.2%. The effects of temperature and photoperiod on wing development of this species were investigated at five constant temperatures (15, 20, 25, 30 and 3590.58C), one ambient (laboratory room conditions) temperature and three photoperiods (16-h, 12-h, and 8-h of light) in the laboratory. The results indicate that both low and high temperatures, and short day-length at lower temperature, tend to accelerate the production of sub-brachypters and brachypters, while high temperature under long photoperiod appears to favour the production of macropters. This ability to produce macropters possibly benefits this bug by enabling rapid dispersal of adults during occasional very dry summers (which may kill preferred weedy hosts) to temporary alternative crop hosts in Canterbury and Central Otago.