Variation in size of male weaponry in a harem‐defence polygynous insect, the mountain stone weta <i>Hemideina maori</i> (Orthoptera: Anostostomatidae)

Abstract

Abstract This study examined intrasexual size variation in the sexually dimorphic mountain stone weta Hemideina maori . We were unable to determine the proportion of weta maturing at different instars, because linear variation in adult head sizes was continuous and not discrete. However, by measuring the growth increment from subadult to adult of weta raised in the laboratory, we estimated that 11% of the males in our main study site were maturing two instars earlier than the largest male. Similar variation in size at maturation has been observed in male Wellington tree weta Hemideina crassidens , which are known to mature at three different instars, but is unusual for insects in general. The variation in head and femur sizes of H. maori was greater between sites (= isolated populations) than within sites, corresponding to an altitude gradient. Females showed a similar altitude gradient, although they showed less variation in body size than males. These data suggest that at any given local environmental temperature, there may be selection for an optimum body size. Whether there is further selection on the smallest males within each site to exhibit alternative mating tactics, as part of a conditional reproductive strategy, remains to be determined.