Family BYRRHIDAE

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Family BYRRHIDAE

Compiler and date details

December 2013 - Dr Federica Turco, Queensland Museum, Brisbane

31 December 1999 - Andrew A. Calder, CSIRO Entomology, Canberra, Australian Capital Territory, Australia

Introduction

Byrrhidae occur worldwide and are almost entirely restricted to the temperate regions of the Northern and Southern Hemispheres with only Chaetophora Kirby & Spence (=Syncalypta Stephens) extending into the tropics. Two subfamilies are usually recognised: Byrrhinae and Syncalyptinae, the latter being sometimes recognised as a family in its own right containing four genera, Chaetophora, Curimopsis Ganglbauer, Microchaetes Hope, and Sierraclava Johnson (see El Moursy 1961, 1969; C. Johnson 1978; Johnson 1982). The family currently contains approximately 30 genera and 350 species worldwide (Lawrence 1991; recent literature). The Australian fauna contains 30 described species and is poorly understood at the generic level. This is a serious underestimate of the size of the fauna as many undescribed species are present in collections. Only three genera have been used for the Australian biota: Microchaetes, Morychus Erichson and Pedilophorus Steffahny. Pedilophorus contains the most described Australian species numbering some 20 species. It is a composite group that requires revision and, as Crowson (1980) has pointed out, many southern species have been incorrectly assigned to Holarctic genera.

Hope (1834) described the first Australian byrrhid from the Swan River Colony, erecting the genus Microchaetes to accommodate it. Boisduval (1835) described another Microchaetes collected on the voyage of the Astrolabe as a Byrrhus Linnaeus from an unknown locality, while Erichson (1842) described Microchaetes scoparius, a species that is abundant in Tasmania. Both King (1869) and Macleay (1871) described a species of Microchaetes each and Blackburn (1889, 1891, 1903) added another five species of which three have turned out to be synonyms of previously described Microchaetes species. Lea (1907) catalogued the Australian and Tasmanian byrrhids describing seven new species which he assigned to Pedilophorus although he noted that there was considerable variation in the vestiture of the beetles, ranging from smooth to tuberculate to hairy. Over the next 13 years Lea was to add another four Microchaetes and nine Pedilophorus to the fauna culminating in a revision of the group (Lea 1920). It should be noted that Lea's concept of the Byrrhidae also included species that are now considered to belong to other families as diverse as Chelonariidae, Sphindidae and Limnichidae. Wilson (1921) was the next to take an interest in the byrrhids describing two new species of Pedilophorus taken by sieving damp moss collected from tree fern trunks and old logs. Oke (1932) was the last person to take an interest in the byrrhids, describing a new Pedilophorus some specimens of which were reported to have been taken from inside a termite's nest at Bacchus Marsh, Victoria. Lawrence et al. (2013) reviewed Australian Byrrhinae, establishing six new genera and giving a key to all byrrhid genera found in Australia.

Byrrhid adults and larvae usually feed on mosses, liverworts and lichens, while some attack the roots of higher plants including wild grasses, oats, clover, various vegetables and lilies in North America (Essig 1958; El Moursy 1961; Watt 1971; Lawrence & Britton 1994; Klimaszewski & Watt 1997). The larvae can be found in the soil, in moss on tree branches and trunks or leaf litter in damp areas. Adults can be found feeding at night on moss covered tree trunks and branches particularly in areas with high humidity. Recently Guy & Gibbs (1985) have recorded that an undescribed byrrhid that feeds on a species of Cardamine in the Australian Alps around Mt Kosciusko transmits a tymovirus, the turnip yellow mosaic virus.

Diagnosis

Adult byrrhids are quite compact, ovoid beetles and when disturbed are capable of retracting their appendages tightly against the underside of their bodies as well as flexing the head ventrally so that they resemble small pebbles or pieces of gravel. This has led to the common name of pill beetles in various parts of the world. They range from 1.5 to 5.5 mm in length and are either dull black or metallic green with tubercles, clothed in bristles or scales or are glabrous. The antennae are 11-segmented and often suddenly thickened towards the apex giving the appearance of being weakly clubbed. The procoxae are transverse with exposed trochantins and the procoxal cavities are open behind both internally and externally. The prosternal process is broad and fits into a cavity on the mesosternum. The mesocoxal cavities are usually widely separated and partly closed by the mesepisternum. The hindwing has a short, oblique, open or closed radial cell and no anal (wedge) cell. There are five visible abdominal sternites, the first two being connate. Segment 8 bears functional spiracles. The tarsi are either 4-4-4 or 5-5-5 and usually have a membranous appendage on segment 3. The legs are often capable of being retracted into cavities on the undersurface (Lawrence & Britton 1991; 1994).

Two distinctive types of byrrhid larvae can be recognised. An ovate, flattened, heavily sclerotised larvae with a short ninth segment and a subcylindrical, more lightly sclerotised larvae with an enlarged ninth tergite. The head has five or six stemmata on each side. The mandibles have a basal brush of hairs, lack a mola and articulated prostheca. The maxillae have well developed lacinia, palpiform galea and large articulating area. Tergite 9 does not have any urogomphi or an operculum. The spiracles are biforous and lack a closing apparatus (Lawrence 1991; Lawrence & Britton 1994).