Does melanism influence the diet of the mountain stone weta Hemideina maori (Orthoptera: Anostostomatidae)?

Melanic and non-melanic mountain stone weta Hemideina maori (Orthoptera: Anostostomatidae) from the Rock and Pillar Range exhibit differential rates of melanotic encapsulation, a response to the presence of pathogens within the body. Because pathogens normally enter the body via food contamination, we hypothesised that dietary differences between the colour morphs might exist. We used faecal pellet analysis to determine the diet of the mountain stone weta. We then tested for differences between the two colour morphs in overall diet composition and the proportional contribution of invertebrate fragments to faecal pellets. The number of invertebrate fragments to the diet did not differ between the two colour morphs. Only when the plant species that were eaten infrequently were given greater weight in an Analysis of Similarity (ANSOM) did significant differences emerge in the diet of the two colour morphs. Hence, there was a weak but significant difference in the overall composition of their diets, but the ecological significance of this difference is unclear. Experimental studies could be used to determine if the dietary differences shown reflect true feeding preferences, or were due to small-scale differences in food availability or stochastic variation.