Ecology

So far as is known all species are fungivores; some are associated with mammal, bird or social insect nests and many occur among leaf-litter in forest environments but in all cases they are known to consume various fungi and any association is due to the presence of fungi rather than the animal hosts. Myrmecophilic and termitophilic species very probably develop on fungi cultivated by the hosts but they may scavenge and develop on incidental fungi growing among nest detritus. Some species are generally associated with ants etc. in the wild e.g. Pleganophorus bispinosus Hampe, 1855 occurs under bark and among moss on various broadleaf trees, usually in association with Lasius brunneus. Insect host associations have been published for about 24 endomychids from 14 genera and 6 subfamilies. Several species have been observed feeding upon leaves and other plant material but in all cases they are otherwise known to be fungus feeders. Associations with various trees and other plants are often found in the literature but these more likely reflect associations between the host fungi and the plants on which the beetles occur. Both adults and larvae may feed upon large fruiting bodies, graze smaller ones or consume mycelia, some feed on spores and some have been observed feeding upon lichens. Very obviously a large number of species will be found by searching around the bark etc. of decaying wood, especially where fungi are obvious, or by sieving litter in wooded environments etc. and many species regularly occur in extraction samples from such situations. Adults of many species are gregarious and may be found by searching nocturnally, sometimes in unexpected situations; Mycetaea subterranea (Fabricius, 1801) occurs in the wild in tree hollows and old bird nests etc. but is also synanthropic occurring in damp cellars and stables etc. where they develop on fungi growing on walls or exposed structural timbers and may develop very large populations. Bird nests are always worth examining as several endomychids e.g. species of Symbiotes and Holoparamecus, are regularly present. More generally a few species are associated with stored products and may become pests as large populations develop, these include species of Holoparamecus, Mycetaea subterranea and Merophysia letourneuxi, and a wide range of products have been recorded including flour, grains, bones, nuts, chocolate, bamboo, wine corks and paper products etc. Trochoiderus desjardinsi has been recorded developing among kapok seeds and coconut husks. Many specific fungal-host associations will be found in the literature and while a few endomychids appear to be restricted to one host e.g. Symbiotes duryi Walton, 1910 or S. impressus Dury, 1912 with Pleurotus ostreatus, or Leiestes seminiger, Gyllenhal, 1808 with Piptoporus betulinus, the majority are polyphagous or oligophagous and some genera are associated with one type of fungus e.g. Lycoperdina with puffballs.

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Description

Endomychids are small to medium sized beetles, 1.0-10.0mm, the majority being 2-7mm, and elongate-oval to almost circular and continuous or discontinuous in outline, moderately convex to flattened and widely explanate. The colour varies widely; smaller species are drab, otherwise black or brown to vividly red or yellow or with coloured patterns or spots, and many are variously metallic. Many are glabrous; when present the pubescence is fine and moderately dense, recumbent to erect and sometimes doubled. Head obvious from above, weakly declined and prognathous, the vertex smooth and variously punctured, rarely with major impressions etc. Frontoclypeal suture present, the clypeus generally quadrate to trapezoidal and narrow, labrum small, quadrate and curved anteriorly, mandibles small, curved and sharp or dentate. Eyes proportionally large and moderately convex, temples generally hidden within the pronotum, antennae 8-11 segmented although sometimes 4 or 5 segmented and modified, usually 11-segmented with a distinct 1-3 segmented club and inserted laterally in front of the eyes, in a few species the number of segments or the form of the club is sexually dimorphic. Labial palps 3-segmented with the terminal segment cylindrical to narrowly triangular, maxillary palps 4-segmented with the apical segment developed; oval to triangular or securiform. Pronotum broader than the head, transverse to weakly elongate and variously explanate, sometimes only in the basal half, and distinctly bordered laterally. Lateral margins very variable, posterior angles distinct and well-defined, anterior angles simple to strongly produced forward, sometimes substantially concealing the head. Surface variously punctured and microsculptured, usually with a pair of elongate basal impressions which may extend forward to the disc or to the anterior margin, or with sub-lateral grooves, in some exotic species with greatly developed structures; tubercles, ridges or spines. Prosternum variable, often long anterior to round, open posteriorly and closed internally, coxal cavities, the process usually long and reaching the mesosternal margin. Mesosternum short with coxal cavities open or closed by the metasternum. Metasternum broad and long anterior to transverse and widely separated coxal cavities, in many with distinct sub-coxal fovea and a median longitudinal impression, basal margin often arcuate either side of the middle and extending between the meso-coxae. Scutellum small to medium sized and generally distinct from above; triangular to truncate or apically rounded. Abdomen with 5 or 6 ventrites; the basal ventrite usually longest and lacking post-coxal lines. Elytra entire and completely covering the abdomen, usually continuously rounded apically and with well-developed and complete epipleura. The surface varies from finely and randomly punctured to strongly punctured and/or striate, in some exotic forms with greatly developed sculpture or very widely explanate, in outline generally broadest about or in front of the middle, curved laterally and tapering to the apex. Legs generally long and slender with concealed trocantins. Pro-coxae convex and circular to slightly transverse, not prominent and usually widely separated. Meso-coxae usually convex, round and widely separated. Metacoxae transverse and widely separated. Trocanters small, femora unarmed although in some exotic species with long and slender spines, tibiae slender with small and obscure spines on the inner apical angle. Tarsi 4-4-4 or 3-3-3, 1-3 variously lobed, in many the third is small and obscured by the lobes of the second. Claws simple and well-developed.

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In temperate regions most species are quite typical although they vary widely e.g. the tiny Symbiotes and Mycetaea are very different from the much larger Endomychus or Lycoperdina and while some larger species e.g. Endomychus coccineus (Linnaeus, 1758) are strikingly coloured, the majority are quite drab and even within a genus the colour can vary widely e.g. Endomychus jureceki Mader, 1936 is entirely metallic blue. The small species of Pleganophorus are unusual in having 4-segmented antennae with the terminal segment greatly enlarged, and generally the rather atypical species of Holoparamecus are distinctive due to their elongate form and strongly constricted pronotum. Tropical species on the other hand can be very different and difficult to appreciate from a familiarity with temperate forms e.g. Neotropical species of Corynomalus Chevrolat, 1836 and southeast Asian species of Cyclotoma Mulsant, 1851 are very convex and rounded, often have long legs are often strikingly coloured and/or metallic. Some Southeast Asian species of Eumorphus Weber, 1801 have very widely explanate elytra and are quite unlike any temperate forms, this is most developed in E. marginatus Fabricius, 1801 and E. halaeus Arrow, 1920. But some of the most strikingly developed species have various pronotal and elytral modifications; some species of the Southeast Asian genus Amphisternus Germar, 1843 e.g. A. vomeratus (Gorham, 1901), have very large and curved horn-like elytral growths in both sexes. Among the most developed are some species of the Neotropical genus Cacodaemon Thomson, 1857; C. hamatus (Guérin-Méneville, 1837) has 3 large and blunt tubercles on each elytron, the entirely black C. satanas (Thomson, 1856) has long, thin legs and long thorn-like projections to the pronotum and elytra and the bizarre C. spinosus (Gorham, 1901) is similarly spined but has a red marking towards the base of each elytron. Similarly the larvae of some tropical species are strikingly developed with long multi-spined and brightly coloured defensive outgrowths.