CRYPTOPHAGIDAE Kirby, 1826
Silken Fungus Beetles
Most species of this large group occur on fungus and rotting plant matter, while others are found on flowerheads where they are often abundant. Some species are also stored product pests.
POLYPHAGA Emery, 1886
CUCUJOIDEA Latreille, 1802
This is a small family of between 600 and 800 described species included in about 60 genera and 2 subfamilies. The majority occur in the Holarctic region and the greatest diversity is in the Palaearctic; about 150 species occur in the Nearctic while the central European fauna includes more than 130 species. Very few occur in tropical regions; about 20 have been recorded from Australasia, 12 from Africa and 15 from the Neotropical region although many genera are in need of revision and many more specimens await description so these figures are likely to change. The Atomariinae LeConte, 1861 includes 3 tribes of which the Hypocoprini Reitter, 1879 has variously been treated as a distinct subfamily, family or as a group of the Cucujidae, it includes 4 genera and about 20 species with the majority occurring in the Palaearctic region; 2 species are Neotropical and 1 occurs in North America. The genus Hypocoprus Motschulsky, 1839 includes 3 species of which H. latridioides Motschulsky, 1839 is the only UK representative of the tribe. Atomariini LeConte, 1861 includes 18 genera, the largest of which, Atomaria Stephens, 1829, contains about 200 species in 2 subgenera; about 60 occur in central Europe while 44 species of both subgenera occur in the U.K. The tribe is Holarctic, extending with a few species in South Africa and other areas. Cryptafricini Leschen, 1996 is a very widely distributed tribe of 5 species in 4 genera; 2 occur in Australia and one each in Asia, Ecuador and Africa. The majority of species are included in the Cryptophaginae Kirby, 1826 which is divided into 4 tribes. The Picrotini Crowson, 1980 occurs only in the Southern Hemisphere; it includes 40 species in 11 genera and is exclusively Australasian and Neotropical. Caenoscelini Casey, 1900 includes 5 genera and more than 50 species and is Holarctic, extending south to Mexico, the greatest diversity is in the Palaearctic region and the UK fauna includes 3 species of Caenoscelis Thomson, C.G., 1863. Cryptophagini Kirby, 1826 is the largest tribe with about 20 genera and is most diverse in the Palaearctic region; both the Australian and African faunas include 8 species and only 2 are known from the Neotropical region, the UK fauna includes 5 genera and more than 50 species, most of which are in the large genus Cryptophagus Herbst, 1792.
All members of the family are small, 0.8-5.2mm although most are between 1.5 and 3.0mm, and among the largest are species of Antherophagus Dejean, 1821 of which 3 are included in the UK fauna. The form varies; most are either elongate, rather parallel-sided and to some degree flattened, or oval and convex, the colour varies from black or rich red-brown to pale testaceous and many are bicoloured or have contrasting maculae etc. Most are distinctly pubescent, usually this is fine and recumbent but sometimes erect or semi-erect and in 2 or 3 distinct layers, and most are devoid of discreet sensory setae. The head is elongate and often retracted into the prothorax to the posterior margin of the eyes, usually smooth and variously punctured, sometimes with a longitudinal impression on the vertex and with (Atomaria Stephens, 1829 and Ephistemus Stephens, 1829) or without (most genera) a distinct frontoclypeal suture. The clypeus is quadrate or nearly so, mandibles curved and sharp, with a distinct internal mola and in some with a dorsal tubercle but without impressed mycangia, labrum transverse; sometimes with a transverse ridge or line and sometimes produced into a median process. Labial palps 2-segmented; equal in width in e.g. Cryptophagini, or with the basal segment distinctly wider in e.g. Atomarinae or Caenoscelini. Antennae almost always 11-segmented with a loose 3-segmented club, the basal segment is wide and conical or rounded laterally, and often curved, intermediate segments often quadrate or slightly elongate and sometimes, as in many Atomaria, with alternating long and short segments. Insertions anterior or lateral in front of the eyes and visible from above, in Ephistemus with antennal grooves under the head and pronotum. Eyes usually convex and prominent, with fine facets and with or without setae, temples short and narrowed to the base but sometimes developed; in the monogeneric Thortus Bran, 1893 from New Zealand they are produced laterally behind the eyes. Pronotum quadrate to transverse, weakly convex, smooth and variously punctured and pubescent, in some Cryptophaginae with distinct fovea towards the base and in some Atomariinae with a transverse depression parallel to the basal margin, lateral margin variable; curved and broadest at the base or about the middle to parallel-sided, with a well-developed marginal bead although absent in Hypocoprini and present only towards the base in some Atomariinae. Base generally as wide as the elytral base, posterior angles not produced, lateral margins variously smooth or toothed; in Cryptophaginae often distinctively toothed near the middle or produced or toothed behind the anterior angles. Prosternum quadrate to elongate in front of rounded and separate, externally open or closed coxal cavities, prosternal process well-developed, arched or flat, broadly rounded to obtuse or truncate apically and often overlying the base of the mesosternite. Mesosternum short with separate coxal cavities closed laterally by the metasternum. Metasternum elongate, without a transverse groove but sometimes with a long median impression, coxal cavities transverse and widely to narrowly separate. Abdomen with 5 free ventrites, basal ventrite longer and usually produced between the metacoxal cavities. Elytra completely covering the abdomen or very nearly so, epipleura well-developed in the basal half only, often absent behind the middle, surface smooth; apunctate to finely or strongly punctured, without striae, at most with ill-defined puncture rows. Legs slender and relatively long. Pro- and mesocoxae recessed into cavities, posterior coxae not recessed to receive the femora. Trocanters relatively long, about one-quarter the tibial length. Femora parallel-sided and straight to weakly curved, sometimes weakly expanded about the middle or towards the apex. Tibiae parallel to weakly expanded towards the apex, without prominent teeth or spurs and generally with 2 small spurs on the inner apical angle. Tarsi 5-5-5, 5-5-4 or 4-4-4, sometimes sexually dimorphic; 5-5-5 in the female and 5-5-4 in the male.
Cryptophagids generally may be recognized by the following combination of characters: small size and in many cases (with a little experience) characteristic appearance, head exposed with the antennal insertions visible from above, antennae with a distinct or gradual 3-segmented club (rarely 1 or 2 segmented), mandibles lacking mycangium, pronotum bordered (except in Hypocoprini), elytra randomly punctured and with well-developed epipleura (at least in the basal half), basal abdominal ventrite longer than the others and mesocoxal cavities closed by the metasternum. Many species of Atomariinae are sexually dimorphic in body shape and antennal morphology. Specific identification can be very difficult and dissection is often necessary. There are no up to date keys to the family in English, Joy’s Handbook will reliably key out to genera and there is a guide to species of Cryptophagus (Coombs, C.W. & Woodroffe, G. E., 1955. A revision of the British species of Cryptophagus (Herbst) Transactions of the Royal Entomological Society of London. 106: 237-282), and beyond this there is an on-line key Here.
Cryptophagid larvae are elongate and parallel-sided or a little wider at the middle and cylindrical or a little flattened, and only lightly sclerotized. Head prognathous and slightly elongate, with well-developed 3-segmented antennae and lacking a frontoclypeal suture. The legs are 5-segmented and relatively long. The abdominal segments bear circular spiracles in the integument, not on tubercles, the ninth tergite usually has a pair of upturned and sharp urogomphi and the tenth segment is well-developed, circular and flat or inclined ventrally.
Cryptophagus sp. larva
Species are generally associated with decaying vegetable matter infested with fungal growth upon which the larvae feed. Some species of Henoticus Thomson, C.G., 1868, Cryptophagus and Atomaria have become pests of stored products which have become infested with fungi and these may occur in huge numbers in barns, granaries, cellars and silos etc. Atomaria linearis Stephens, 1830 is a common pest of sugar beet etc., overwintered adults emerging and ovipositing among developing young plants may do considerable damage. More typically species of Atomaria live among mouldy vegetation or, less often, among fungi on trees, in dry dung or under bark. Many species of Cryptophagus may also be found under bark. Many species may be found by general sweeping, extracting samples of vegetation, at light or from flight-interception traps, sieving old fungi and bark etc., especially in the autumn, may also be productive. Many host-specific associations have developed e.g. species of Antherophagus Dejean, 1821 are phoretic on humble bees, they may be found on flowers where they consume pollen, but they attach to bees and are transported to the nest where they oviposit among debris and where the larvae develop at the base of the nest consuming organic debris and droppings. Species of Hypocoprus have been found among dung on sandy substrates and also in ants nests, Ootypus globosus (Waltl, 1838) is almost always recorded from dung and may occur in large numbers while species of Ephistemus Stephens, 1829 are more general, occurring in dung but also from decaying vegetation generally and often abundant in compost heaps. Adults of Telmatophilus Heer, 1841 are associated with marginal vegetation; T. typhae (Fallén, 1802) among the flowers and between the layered leaves of Typha, and T. schonherrii (Gyllenhal, 1808) from Typha and Sparganium. Species of Micrambe Thomson, C.G., 1863 are more saproxylic; M. bimaculata (Panzer, 1798) occurs among the bark of both coniferous and deciduous trees infested with fungus while M. ulicis (Stephens, 1830) and M. woodroffei Johnson, 2007 develop in decaying gorse stems, and the very local and rare M. pilosula (Ericson, 1846) has been found in thistle stems. Paramecosoma melanocephalum (Herbst, 1793) and Pteryngium crenatum (Gyllenhal, 1808) occur among decaying bracket fungi on tree trunks. Species of Caenoscelis Thomson, C.G., 1863 may be found by sweeping vegetation. Many species occur incidentally in the nests of mammals, birds and social insects but some may be more specific; Cryptophagus micaceus Rey, 1889 occurs in the nests of hornets and other tree-nesting hymenoptera, and Spavius glaber (Gyllenhal, 1808) occurs in the nests of Formica ants. Species of Atomaria will be found by sweeping vegetation generally, especially in the evening, but many species are more specific regarding habitat and may occur in salt marshes, at sap, among leaf-litter or under the bark of conifers or deciduous trees.
All photos on this page © Lech Borowiec