Observations of the biology and immature stages of the sandgroper Cylindraustralia kochii (Saussure), with notes on some congeners (Orthoptera: Cylindrachetidae)

WA Museum Records and Supplements | Updated 1 years ago

ABSTRACT – Field and laboratory observations of Cylindraustralia kochii are presented with notes on some congeners. Nymphs and adults create galleries in moist soil by compression of the soil with their powerful fore legs, burrowing to depths of up to 1.9 m. During the cooler months and 1-2 days after rain, sandgropers commonly burrow long distances close to the soil surface producing conspicuous raised trails. Adults and nymphs of various sizes were found throughout the year. Eggs and early immatures of the genus (and family) are described for the first time. Pedicellate eggs of C. kochii were suspended singly in closed chambers 40-190 cm deep in moist soil. A 'larval' stage hatches from the egg and moults to a first instar nymph while still in the egg chamber. Five nymphal instars are indicated by morphometric and morphological data. Eggs are laid from autumn to spring but hatching was only observed in mid summer. A duration of at least 12 months is indicated for first instar nymphs, so the complete life cycle may extend over several years. Examination of gut contents revealed that sandgropers are omnivorous, consuming a wide array of plant, fungal and arthropod material. Plant food included root, stem, leaf, flower and seed tissue. Cannibalism occurred in one very dense population of C. kochii. Otherwise, no insect predators or parasitoids were encountered. Associated organisms included gregarines and Amoeba (Protista) in the intestines, rhabditid nematodes in the genital chambers of adults, and six species of mesostigmatid and astigmatid mites which adhered externally to the body. Nymphs and adults produce an odorous, probably defensive secretion from a pair of abdominal glands.

Key words: subterranean insects, ethology, ecology, parasites

Author(s) Terry F. Houston
Records 23 : Part 3
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