FNZ 23 - Dolichopodidae (Insecta: Diptera) - Introduction
Bickel, DJ 1992. Sciapodinae, Medeterinae (Insecta: Diptera) with a generic review of the Dolichopodidae. Fauna of New Zealand 23, 74 pages.
(
ISSN 0111-5383 (print),
;
no.
23.
ISBN 0-477-02627-3 (print),
).
Published 13 Jan 1992
ZooBank: http://zoobank.org/References/E732CABA-8771-4F37-8B28-B4FF68B170E9
Introduction
The Dolichopodidae or 'long-legged flies' comprise one of the most diverse fly families. Its diagnostic features include: vein Sc usually joined with R1, crossvein r-m in the basal quarter of the wing, and wing cells dm and bm united or only incompletely separated. Wing vein M is usually unbranched, but vein M2 is present in the subfamily Sciapodinae. However, most dolichopodids are readily recognised by their general habitus, slender build, long legs, often metallic blue-green coloration, and hair-like arista.
Although good fliers, dolichopodids are frequently cursorial on foliage, tree trunks, mud flats, intertidal reefs, and river rocks. They favour moist habitats, and are often taken in large numbers in Malaise traps and yellow pan traps, as well as by sweeping.
Adults are predatory on such soft-bodied invertebrates as mites, thrips, psocids, aphids, small nematocerous Diptera, and aquatic oligochaetes, and are important general control agents of many pest species. Prey is crushed between a pair of longitudinally opposed labella, and the body fluids are ingested through tube-like pseudotracheae.
Dolichopodids are known for their elaborate male secondary sexual characters (MSSC), assumed to aid species recognition during courtship. These MSSC, which often show parallel development in unrelated groups, include flag-like flattening of the arista and tarsi, modified setae and cuticular projections, prolongation and deformation of podomeres, orientated silvery pruinosity, and modified venation. In some instances male-female dimorphism is so striking that the association of sexes is not readily apparent.
The hypopygium or male genital capsule is often enlarged, and often is diagnostic for species identification. In some groups the hypopygial peduncle - formed from the 7th abdominal segment - is prolonged, and the hypopygium is projected forwards underneath the abdomen.
The maggot-like larvae are found in soil, moss, decaying vegetation, and mud, and under bark. Most larvae are predators or scavengers, although Thrypticus is a phytophagous stem miner in various grass-like monocotyledonous plants. Almost nothing is known of the immature stages of New Zealand species.
Robinson & Vockeroth (1981) provided a well illustrated synopsis of the family, and Dyte (1959) reviewed the immature stages.
Historical summary
The study of New Zealand's Dolichopodidae began with the description of a single species by Walker (1849). Subsequently, Hutton (1901) described four species of Sciapodinae and two additional New Zealand species, including the endemic genus Ostenia. Species from the Bounty Islands and Macquarie Island were treated by Lamb (1909).
Becker (1924) described two species of New Zealand Sciapodinae in a paper on Dolichopodidae of Formosa. Since neither the paper's title nor the 'Zoological Record' for 1924 gave any indication that New Zealand species were included, their existence remained unknown to both Parent (1933a, b) and Miller (1956). C.E. Dyte alerted me to these 'lost' species.
Parent's (1933b) monograph on the New Zealand Dolichopodidae is the standard reference. It is perhaps one of his best works among numerous papers on the family, and it added 103 species and eleven genera to the fauna.
Since Parent, the New Zealand fauna has remained little studied except for nomenclatural notes by Miller (1945) and descriptions of Campbell Island species by Oldroyd (1955) and Haxrison (1964). The Bickel & Dyte (1989) catalogue of Australasian and Oceanian Dolichopodidae covers all described species and nomenclatural changes.
New Zealand's Dolichopodidae
The New Zealand subregion (see map on p. 71) has 132 valid species of Dolichopodidae in twenty-eight genera. In diversity among dipteran families it ranks fourth in the fauna, after the Tipulidae, Mycetophilidae in a broad sense, and Tachinidae (based on Evenhuis 1989). However, if the approximately 50% increase in the subfamily Sciapodinae treated here is an indication, the true number of New Zealand dolichopodid species could exceed 200.
Hennig (1960) provided an extensive review of the zoogeography of New Zealand flies and discussed major groups as to their relationship with other southern landmasses, in particular Australia and southern South America He referred to taxa having such austral distributions as AS- groups (A = Australia and New Zealand, S = South America). Hennig emphasised the necessity to demonstrate repeated occurrence of sister-taxa among AS-groups before direct trans-Antarctic links could be assumed. He noted that many AS-taxa also occur or are present as fossils in the Northern Hemisphere.
Hennig did not discuss the Dolichopodidae. However, apart from endemic genera, much of the New Zealand fauna is included in near-cosmopolitan genera: Medeterinae - Thrypticus; Hydrophorinae - Hydrophorus and Thinophilus; Dolichopodinae Hercostomus; Diaphorinae - Chrysotus and Diaphorus; Sympycninae - Chrysotimus and Syrnpycnus; unplaced - Achalchus. Most of these species fit well into traditional generic concepts. Nevertheless, some of these genera, such as Hercostomus and Sympycnus, are broadly defined and need further clarification with respect to the New Zealand species. In this respect, for example, Parent originally placed species now included in the trans-Tasman genus Parentia into three poorly defined genera, Chrysosoma, Condylostylus, and Sciapus.
In terms of generic composition the New Zealand fauna .is continental, but decidedly southern temperate, especially noting the dominance of the Sympycninae. It is broadly similar to the faunas of southem South America (Van Duzee 1930) and Tasmania / southern Australia (Parent 1932a). In sharp contrast to Australia, however, New Zealand totally lacks elements of tropical Oriental-Papuan affinity. Its southerly geographical position has prevented entry of even widespread Indo-Pacific tramp species such as Medetera grisescens de Meijere and Chrysosoma leucopogon Wiedemann, which have both reached New Caledonia. I have seen a small collection of dolichopodids from Raoul Island, Kermadec group (BMNH), comprising Achalcus sp. and Diaphorus sp., which are of New Zealand affinity. The faunas of the southern subantarctic islands appear to be derived from mainland New Zealand.
The relationship of the largely undescribed New Caledonian fauna awaits further investigation. However, New Zealand does not appear to have been a source area for any Polynesian group, nor for Lord Howe or Norfolk islands, the dolichopodid faunas of which are of direct Australian affinity (Bickel, in press).
New Zealand has fifteen endemic dolichopodid genera, of which ten are monotypic. They fall into three categories, as follows.
- Distinctive genera derived from ancestral stocks within New Zealand, e.g., Ostenia (Diaphorinae), Halteriphorus (Neurigoninae), Scorpiurus and Helichochaetus (Hydrophorinae), Apterachalcus (f'rom Achalcus), and Scelloides / Ischiochaetus (Sympycninae).
- Genera based only on striking MSSC which don't deserve separate generic status, both because females cannot be distinguished from the source genus, and other species with less spectacular MSSC are not generically separated. For example, Colobocerus is distinguished only by male antennal shape, and should be included within Sympycnus.
- Primitive relicts or genera of uncertain affinity, such as the newly described Naufraga.
For additional biogeographical information, see Remarks under Parentia, Austrosciapus, and Thrypticus.