Biology and ecology of the New Zealand mole cricket Triamescaptor aotea Tindale (Orthoptera:Gryllotalpidae)

Abstract

Distributions of the subfamily Gryllotalpinae (Orthoptera:Gryllotalpidae) and the New Zealand species Triamescaptor aotea (Tindale), are described. A field population of T. aotea at Lake Pounui Reserve, western Wairarapa, was studied to determine features of its habitat, behaviour and life history. Burrowing activity is discussed including the natural structure of burrows in the field, which was determined using a newly devised molten wax cast method. Burrows consist of shallow surface tunnels which lead into a main burrow system which forms a ring. The ring was present in all burrows of T. aotea examined and in adult females and egg brood chamber is constructed for oviposition. The burrow continues down from the ring tapering to a dead end. The burrow structure is compared with those of other genera of the subfamily, and found to resemble those of other mole crickets where the female is known to brood eggs and nymphs. The simple burrow entrance of T. aotea differs from that of stridulating mole crickets in which the entrance is specialised as an amplifying device. The feeding activity is described and T. aotea was found to have an opportunist omnivorous diet being predominately carnivorous. This diet was most similar to the omnivorous diets (with a predominance of animal material) in other Gryllotalpinae. T. aotea was found to prefer habitats with light soils in low lying areas that are moist throughout the year, thus making it similar to other mole crickets in the subfamily. T. aotea is active in winter unlike corresponding continental and northern hemisphere species which hibernate. The external and reproductive morphology is described and compared with other genera of the subfamily and the systematics of T. aotea are discussed with reference to the conclusions of Tindale (1928). Development of egg clutches, and nymphs was determined by field sampling and laboratory rearing. Eggs are laid in mid to late November and hatch about 30 days later. The life cycle was found to be 2.5 to 3 years long and was found to be most similar to the genera Gryllotalpa with nymphs being helpless requiring parental care. Scapteriscus species have a shorter, univoltine life cycle with early nymphs being more active and do not exhibit parental care.