Hendelia

Introduction

Hendelia Czerny is pantropical and south temperate in distribution with 44 described species (Lonsdale & Marshall, in manuscript). It is the sister genus to the north temperate Clusiodes, with whom it shares a clear north/south division, although the type species (H. beckeri Czerny) is widespread in the Palaearctic. 

Caloren & Marshall (1998) recently described the behaviour, biology and faunistics of the New World Clusiodes and Hendelia, and Rohácek (1995) described that of H. beckeri in the Czech and Slovak Republics. Adults of Clusiodes and Hendelia are found predominantly on hardwood, but several Clusiodes have been collected off of softwood trees such as pine, hemlock and fir (Caloren & Marshall, 1998; Rohácek, 1995;Withers, 1985). Species of both genera have been reared from puparia collected in numerous species of rotting deciduous tree trunks including alder, aspen, ash, beech, birch, elm, hornbeam, maple, poplar and tulip trees (Withers, 1985; Greve & Midtgaard, 1986; Rohácek, 1995; Caloren & Marshall, 1998).

A number of Hendelia have strikingly modified heads (presumably associated with male agonistic behaviour), such as the pale excavated head and flattened arista seen in H. beckeri males, the elongate antennae of H. extensicornis Frey, the strongly widened head and corkscrewed vibrissae of several Australian species, and the elongate genal processes of the neotropical H. mirabilis (Frey) and H. kinetrolikros (Caloren & Marshall) (Caloren & Marshall, 1998; Marshall, 2000; McAlpine, 1976). Several of these species have been observed while engaged in male agonistic behavior at lek sites, usually on exposed tree trunks. Tuomikoski (1936) observed the pre-mating behaviour of H. beckeri, where males held their fore legs and "shivered" the fore tarsi when approaching females, using them as feeler-like organs.

In addition to bare patches of wood, we have found that small dung baits attract adults of Clusiodes and Hendelia in the New World.

Characteristics

Species of Hendelia usually range from 3.0-5.3 mm (rarely less than 3.5 mm) in length, but several Old World species are 2.3-2.5 mm and are among the smallest clusiids. Like its sister-genus Clusiodes, Hendelia species have reduced anterior and posterior fronto-orbitals, interfrontal bristles, well developed medial genal bristles, swollen spermathecal ducts, a large subapical disc on the ventral receptacle, a longitudinal desclerotization on the female seventh sternite, a crested fin-like phallapodeme, a distiphallus that is rod-like basally with a membranous distal section and an elongate pregonite that is perpendicular to the long axis of the hypandrium (Lonsdale & Marshall, in manuscript).

Hendelia is entirely defined by male genitalic characters (perianal area longer than wide; surstylus usually small, lobate and perpendicular to the long axis of the epandrium; ejaculatory apodeme widest apically), but it is most easily separated from Clusiodes by retained ancestral states: the arista is variably plumose or laterally compressed (never pubescent); if 3 fronto-orbital bristles are present, the anterior two pairs are usually closely spaced near the anterior margin of frons; the male fore and mid femora have one anterior and one posterior row of ventral ctenidial bristles (never two posterior rows); the scutum never has a white lateral stripe (Lonsdale & Marshall, in manuscript).

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Hendelia head morphology. Hendelia beckeri Czerny, male; H. beckeri, female; Hendelia latifrons (Frey), female. © Owen Lonsdale.

Hendelia beckeri Czerny: male external genitalia, posterior and left lateral (left); male hypandrial complex, left lateral (centre); female internal genitalia (right). © Owen Lonsdale

Phylogenetics

Hendelia and Clusiodes Coquillett form a natural group, supported by the synapomorphies listed above, and are considered to be monophyletic with Heteromeringia Czerny and Tranomeringia Sasakawa on the basis of telescoped and darkly pigmented spermathecae (Lonsdale & Marshall, 2006b).

In an upcoming revision of Clusiodes (Lonsdale & Marshall, in manuscript), previously unrecognized male genitalic characters (see above) are used to redefine Hendelia.  This redefinition will drastically alter Hendelia's boundaries, which will encompass not only the seven species previously placed in Hendelia, but 33 species of Clusiodes (almost all tropical and south temperate species previously placed in that genus), all three species of Prohendelia Frey, and the monotypic Xenoclusia Frey.

Several revisions of Hendelia are currently being developed.

References

Caloren, D.C. & S.A. Marshall. 1998. A revision of the New World species of Clusiodes Coquillett (Diptera: Clusiidae). Studia Dipterologica 5:261-321.

Greve, L. & F. Midtgaard. 1986. The Clusiidae (Diptera) from the islands H??ya and Ost?ya in the Oslofjord and a survey of the family in Norway. Fauna Norvegica Series B 33: 86-92.

Lonsdale, O. & S.A. Marshall. 2006b. Revision of the New World Craspedochaeta Czerny. Zootaxa 1291: 1-101.

Marshall, S.A. 2000. Agonistic behaviour and generic synonymy in Australian Clusiidae (Diptera). Studia Dipterologica 7: 3-9.

McAlpine, D.K. 1976. Spiral vibrissae in some clusiid flies (Diptera: Schizophora). Australian Entomological Magazine 3(4): 75- 78.

Roh?cek, J. 1995. Clusiidae (Diptera) of the Czech and Slovak Republics: Faunistics and notes on biology and behaviour. Cas. Slez. Muz. Opava (A) 44: 123-140.

Tuomikoski, R. 1936. Bemerkungen ?ber die Clusiiden (Dipt.) Finnlands. Annals Entomologici fennici 2(4): 182-186.

Withers, P. 1985. Notes on some British Clusiidae and reduction of Clusiodes facialis (Coll.) to synonymy. Proceedings of the Transactions of the British Entomological Natural History Society 18: 63-64.