The clawless upside-down fly, Nothoasteia clausa (Diptera: Neurochaetidae): notes on distribution, behaviour, and comparative morphology David K. McAlpine The minute fly Nothoasteia clausa McAlpine, 1988a, is known only in temperate Western Australia, where it is closely associated with the host plant Xanthorrhoea preissii (Xanthorrhoeaceae). Its cursorial behavior is compared with that of other taxa of the Neurochaetidae (upside-down flies), and contrasted with that of Stenomicra spp. (Periscelididae) in a similar habitat. Some morphological features are very unusual in cyclorrhaphous Diptera, and attention is here given to the attachment of the fore coxa to the thorax, the reduction of the tarsal claws, and several features of the male postabdomen. D.K. McAlpine, Australian Museum, 6 College Street, Sydney, NSW, 2010, Australia. Introduction Museum 2011). While consideration of combined The small acalyptrate family Neurochaetidae behavioral and morphological data adequately con- (upside-down flies) includes the extant genera Neu- firms the position of Nothoasteia in the Neurochaeti- rochaeta McAlpine, 1978 (Australasian and Oriental dae, the genus possesses some extraordinary apo- regions), Neurocytta McAlpine, 1988a (Africa - Zim- morphies, e.g. the reduced and non-functional tarsal babwe), Neurotexis McAlpine, 1988a (Madagascar), claws and the structural transformation of the epan- and Nothoasteia Malloch, 1936 (Australia); also the drium and associated parts of the male postabdo- fossil genus Anthoclusia Hennig, 1965 (early Tertiary men – both conditions not approached in any other - Baltic Amber). See McAlpine (1993), for a generic schizophoran fly known to me. Comparative study key and main references. of other morphological conditions in Nothoasteia The Neurochaetidae are characterised (for the four has led to a fuller understanding of character states extant genera) by unusual cursorial behavior (con- seen in the other extant neurochaetid genera and in stantly facing downwards while moving on a vertical outgroups to the Neurochaetidae (McAlpine 1993). or steeply sloped surface) and by unusual morphol- For general appearance of Nothoasteia clausa see ogy of the antenna, thorax, and abdomen. McAlpine Fig. 1 herein and Marshall (2008: 425; photo of liv- (1988b) interpreted certain behavioral and morpho- ing male). logical traits of neurochaetids as adaptations to a Apart from Nothoasteia clausa, the only other well somewhat unusual ecology. known Australian species of the family is Neurochaeta The genus Nothoasteia was till recently only known inversa McAlpine, 1978, which lives in higher rain- from the holotypes of the two included species, fall areas of New South Wales and Queensland. The N. platycephala Malloch, 1936, and N. clausa McAlp- ecology, behavior, and life history of this species were ine, 1988a. Males of these species are not previously treated by McAlpine (1978). See McAlpine (1988a, described. More recently received information on 1988b) for further information on Neurochaeta, and the habitat of N. clausa in south-western Australia McAlpine (1993) for information on Afrotropical has led to some familiarity with this species both in neurochaetids. the field and in the laboratory collection (Australian Tijdschrift voor Entomologie 154: 159–165, Figs 1–10. [ISSN 0040-7496]. http://www.nev.nl/tve © 2011 Nederlandse Entomologische Vereniging. Published 1 December 2011. Downloaded from Brill.com09/26/2021 08:15:26PM via free access 160 Tijdschrift voor Entomologie, volume 154, 2011 Fig. 1. Nothoasteia clausa, female, Yalgorup National Park, Australia. Legs are arranged to show exact proportions of parts. [Scale = 1 mm]. Distribution collectors to find more specimens in Queensland Nothoasteia clausa is only known from temperate and New South Wales, particularly on plants of Xan- parts of Western Australia. Relevant localities prob- thorrhoea spp., have been unsuccessful. ably all have an average annual rainfall of at least 600 mm, and are indicated in Fig. 2. Because avail- able material of N. clausa has been obtained by a Behaviour and ecology of Nothoasteia few entomologists visiting Western Australia for Adults of N. clausa were often numerous but appar- brief periods, this map indicates our locality records, ently not gregarious among leaf bases deep in the rather than the definitive distribution of the species. crowns of Xanthorrhoea preissii in natural bush The records extend from Yanchep district in the habitats or roadside vegetation. They were found north, the sea coast in the west, and King George’s by carefully parting the foliage and searching with a Sound (or Albany district) in the south-east. Travel- low-magnification binocular magnifier. In all cases, ling between these limits, B.J. Day and the author except when injured, the flies maintained a head- found adults of N. clausa on every substantial stand downwards orientation (as in other neurochaetids) of Xanthorrhoea preissii Endlicher (family Xanthor- and either dodged among the leaf bases or ran rhoeaceae) investigated in November–December outwards towards the leaf tips before taking flight. 1998. See Western Australian Herbarium (2011) for When running outwards along a slender leaf (no habitus illustration of this plant. Voucher specimens more than c. 3 mm wide) the fly’s body remained have been placed in the Australian Museum, Sydney, parallel with the long axis of the leaf. Thus, when the and other institutional collections. leaf tip drooped downwards, the fly was for a short Nothoasteia platycephala Malloch, 1936, the only time head-uppermost. other species of the genus, is known only from When aspirated and placed in a glass tube the flies the damaged holotype from Brisbane, Queens- continued in the head downwards position, whether land (in Australian Museum, Sydney). Attempts by stationary or moving, but did not always respond Downloaded from Brill.com09/26/2021 08:15:26PM via free access McAlpine: Notes on Nothoasteia clausa 161 P 320 T 330 3 4 340 A 350 1150 1160 1170 1180 Fig. 2. Map of southwestern Western Australia, show- ing distribution records for Nothoasteia clausa [A, Al- bany; P, Perth; T, type locality near Dwellingup]. immediately to inversion of the tube, as do Neuro- 5 6 chaeta species. Also, they did not exhibit the diffi- Figs 3–6. Right fore coxa of neurochaetid flies. – 3, An- culty of moving from a wall to a ceiling substrate thoclusia sp., Baltic amber; 4, Neurocytta prisca (McAlp- shown by Neurochaeta species (see McAlpine 1988b ine, 1978), Chimanimani National Park, Zimbabwe; for N. parviceps McAlpine, 1988a; similar restrictive 5, Neurochaeta inversa, Bellingen, Australia; 6, Nothoast- behavior since observed by the author for N. inversa). eia clausa, Dunsborough, Australia. I think it probable that the as yet unknown larvae of Nothoasteia clausa live on or in the Xanthorrhoea plant, and, by comparison with those of Neurochaeta be a locally endemic species. Stenomicra spp. are inversa (see McAlpine 1978), their location in the sometimes confused with neurochaetids in the field moist or humid environment among the compacted because of their specialized cursorial behavior with leaf-bases in the centre of the crown seems most constant orientation to gravity, but always with the likely. Finding larvae in this location may involve head uppermost (see McAlpine 1978; similar curso- destruction of one or more plants, perhaps at a moist rial behavior since observed by author for numerous season of the year, and should be carried out with Stenomicra spp. in several countries). permission from the appropriate authority. Kingia australis R.Brown is a plant of similar habitus to X. preissii though sometimes placed in a separate Notes on morphology family (Dasypogonaceae). Where K. australis was The general outline of the morphology of Nothoast- growing in association with X. preissii near Pember- eia clausa is indicated in the taxonomic descrip- ton, I could find adults of N. clausa only on the lat- tion by McAlpine (1988a), and antennal structure ter plant species. However, a few minute flies of the is described by McAlpine (2002, arista only) and periscelidid genus Stenomicra Coquillett, 1900, were McAlpine (in press). The general features of the found in the leaf-crowns of K. australis, though these adult insect are shown in Fig. 1. Notable features were nowhere found on X. preissii. These appear to include the relatively large, flattened head with be distinct from Stenomicra spp. collected in other narrow, horizontal eyes, the unusual proportions states of Australia on different host plants, and may of the leg parts, and the wing venation, the latter Downloaded from Brill.com09/26/2021 08:15:26PM via free access 162 Tijdschrift voor Entomologie, volume 154, 2011 Figs 7, 8. Apex of fore tar- sus of neurochaetid flies. – 7, Nothoasteia clausa, near Yalgorup, Australia; cv 8, Neurotexis primula McAlpine, 1993, Ivolaina Zoo, Madagascar. [c, tarsal claw; cv, claw vestige. Scales = 10 µm]. 7 c 8 including fusion of the second basal and discal cells shorter than tergite 5, and sternite 6 is unreduced (as in Neurotexis), instead of the second and first and shaped like sternite 5. basal cells (as in Neurochaeta). Further attention is The fore coxa. The fore coxa of Nothoasteia clausa is here given to structure of the fore coxa, the tarsal remarkable for its longitudinal attachment to the claws, and the male abdomen. thorax (Fig. 6), instead of the somewhat oblique Some morphological features of Nothoasteia and basal attachment occurring in most Diptera. In N. other neurochaetids, that appear to be adaptations clausa the membranous basal socket occupies at least to their specialized biology, were mentioned by 90% of the length of the coxa. This means that, for McAlpine (1988b). an insect adapted to fit into shallow, slit-like cavi- Whole specimens are easily sexed under the micro- ties, less height is occupied by the coxa. On the other scope. The male has a large, tapering tergite 6 hand, the mobility of the coxa is more restricted than (i.e. the last visible tergite before the compact geni- in most flies, so that it can do little more than rock tal segment), which is distinctly longer than tergite from side to side.