Records of the Western AustralIan l'1/!useum 23: 2192c14 Observations of the biology and inlmature stages of the sandgroper Cylindraustralia kochii (Saussure), with notes on some congeners (Orthoptera: Cylindrachetidae) Terry F. Houston Western Australian Museum, Locked Bag 49, Welsh pool DC Western Australia 6986, Australia Email: terry.houstonrilmuseum.wa.gov.au Abstract Field and laboratorv observations of Cvlindraustralia kochii arc presented with notes on some congeners. Nymphs ~nd 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) arc described for the first time. Pedicellate eggs of C kochii were suspended sIllgly in closed chambers 40-190 cm deep III moist soil. A 'larval' stage hatches from the egg and moults to a first instal' nymph while still in the egg chamber. Five nymphal instars are indicated by mc)rphometric and morphological data. 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 INTRODUCTION Fourteen species are Australian, one is Argentinean Sandgropers, once regarded as degenerate mole and one putatively occurs in New Guinea. Cunther crickets (e.g., Tindale 1928), are now classified with erected a new genus, Cvlindraustralia, to contain 13 the short-horned grasshoppers (suborder Caelifera) of the Australian species. Prior to his revision, all and form the family Cylindrachetidae within the known Australian species were placed in superfamily Tridactyloidea (Rentz 1996). Included Cylindracheta Kirbv, a genus Cunther restricted to with them in this superfamily are the Tridactylidae one species from the 'Top End' of the Northern ('pygmy mole crickets') and Ripipterygidae ('mud 'rerritorv. CvlindraustraJia species occur widely crickets') (Cunther 1994; Flook et '11. 1999). All across the Australian continent but are absent from cylindrachetids are burrowing insects, highly the south-eastern portion. modified for a subterranean existence. The body Although the taxonomy of cylindrachetids has shape is cylindrical, the fore legs are highly been reasonablv well studied, their biology has modified for digging, the reduced mid and hind received scant attention (Barrett 1928; Tindale 1928; legs recess into the sides of the abdomen, simple Richards 1 C;i.inther ]992; Rentz 1996). Some eyes replace the compound eyes, antennae and cerci published information is misleading or incorrect are reduced, and wings are entirely absent and nothing has been recorded hitherto of the eggs 1 Of all the orthopteroid insects, thev are and earlv immature stages. Of course, living almost considered to be the most stronglv modified whollv subterranean lives, the insects are rarelv morphological Iv for a subterranean life (Kevan observed and make difficult subjects for study. 1989). In \Vestern Australia, sandgropers have gained a In the most recent revision of the family (Ci.inther reputation as agricultural pests, being reported to 1992), three genera and 16 species were recognized. damage wheat, barlev, oats, sweet lupins and 220 T.F. Houston Figures 1-5 Cylindraustralia kochii. (1-2) Adult female and male, respectively (note bands of pigmentation around abdomen, in male interrupted dorsally on segments 7-9). (3) Last stage nymph (note absence of abdominal pigmentation; dark 'marks' along dorsal median line are gaps in underlying fat body visible through transparent integument). (4-5) Surface trails produced by adults burrowing just beneath surface of ground: (4) simple trails in natural bushland; (5) branched trails on compacted sand surface of farm road. tagasaste between Perth and Geraldton (Richards The present study was undertaken in an attempt 1980; Rentz 1996; Wiley 2000). Only anecdotal and to elucidate the life histories, behaviour and ecology circumstantial evidence, though, was produced by of sandgropers. these authors to show that sandgropers were the cause of the observed plant damage. While the insects themselves are rarely MATERIALS AD METHODS encountered, their characteristic trails (Figure 4) are Over 900 spirit-preserved specimens of a common sight on bare sandy ground in Western Cylindraustralia in the collection of the Western Australia. Two species (C kochii (Saussure) (syn. Australian Museum were examined in this study. psammophila (Tindale)) and C tindalei Giinther) Most were collected by the author from 2002-2005, are known to be extant in and around Perth. the remainder being donated by members of the Biology of sandgropers 221 farming communitv and the general public in Ilorrocks and Creat Sandv Desert sites could not be response to a n1l'dia appeal. Bv far the bulk of the matched to all\' of Clinther's taxa and appear to material studied was comprised of C kochii while represent undescribed species referred to below as most of the remainder consisted of C. tindalci. 'Species A' and 'Species 6', respectively. Although sandgropers have occasionallv been The pronotal width of all specimens was found in pitfall traps, the author's deplovnwnt of measured to determine the number of instars. The gutter traps and pitfall traps combined with drift pronotum is a rigid structure that is easily and fences at a number of sites failed to vield specimens. reliably measured across its greatest width. Following on foot close behind farm ploughs Population sampling at the Dandaragan site was turning over soil under pasture vielded mall\' undertaken approximately every second month specimens. Others were obtained from near-surface although the October sample was not in sequence galleries: bv driving back and forth along sandv with the rest. The method used was to excavate a roads and firebreaks on the margins of bushland large pit at least 1 x 2 m in area and 1-2 m deep shortlv after rain, it was possible to recognize fresh using a spade and trowel and to collect every tra ils where tlll'v. crossed the vehicle's tvre. tracks specimen encountered as the soil was turned over. (Figure 5). Most specimens obtained for this studv, Excavation required 2-4 days. however, were turned up by digging with a spade beneath pastures and weeds on farms. Studv sites where significant work was OBSERVAnONS AND DISCUSSION undertaken are as follows (short-hand names used in this paper appear in quotation marks): l.ife Stages and Morphology "Dandaragan site" Annamullah Farm, 6 km NNE of [)andaragan, 3038'5, ] 1S45'E; 'Tiorrocks site" ­ Adults Willi Culli North Farm, ]8 km W of Northampton Apart from having completely developed (2 km E of Horrocks), 28"22'S,11427E; "Eurardv genitalia, adults are distinguishable from nymphs site" - Eurardy Station, 89 km N of Northampton, in having the abdominal integument wholly or 2734'5, 11440'E:; M. and D. Webb's farm, 23 km E largely tan-coloured (Figures 1, 2) (in males of C. of Northampton, 28"18'52"5, ]] 4'51 '58"E; and kochii the tan pigmentation is usually broken by "Creat Sandv Desert", various sites approximately narrow, colourless, intersegmental bands). The 220-280 km SE of Broome, between 19'04'13"5, abdominal integument of all nymphal stages, by 12344'05"E, and]91752"5, 124'26'2TE. contrast, is completely colourless and, being Various methods of killing and preserving transparent, the abdomen appears white or cream specimens were trialled. For the purposes of later because of the underlying fat body (Figures 3,11). dissection, best results were obtained by freezing Males and females are similar in size. Among a specimens. Where this was impractical, freshlv sample of C. kochii adults from the Dandaragan killed specimens were injected with and stored in site, pronotal widths of males ranged from 6.75­ 10'\, formalin (although injection caused the 8.20 mm (mean 7.35 ± 0.33, n = 20) and of females abdonll'n to inflate and extend). Several specimens from 6.80-8.30 mm (mean 7.4 ± 0.44, n = 14). The were killed bv spraving the head and thorax with sexes are also very similar morphologically but can electrician's freezer and were then immediatelv be distinguished bv the external genitalia. As dissected in saline to check for living parasites or Clinther (] 992) noted, males possess a pair of short, comnwnsals in the gut, abdominal cavitv and stout spines on the paraprocts near the insertions of genital tracts. the cerci (Figure 13). Females lack these spines and, I.ive specimens were maintained in containers of instead, possess a pair of rudimentary gonovalves, moist sand or sandv loam with various plants: Cape the tips of which sometimes protrude slightly Weed (Arctotheca calendula), Wild Oats Fe'na bevond the apical margin of the 8'h abdominal ti1tua), and seedlings germinated from commercial sternite (58, Figure ]2). In C kochii (but not other 'mixed budgie seed'. Class-bottomed and clear species), adult males are further distinguished by a plastic containers permitted observations of large unpigmented patch on the dorsal side of burrowing activitv.