Carcinops pumilio (Erichson, 1834)
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POLYPHAGA Emery, 1886
HYDROPHILOIDEA Latreille, 1802
DENDROPHILINAE Reitter, 1909
Carcinops Marseul, 1855
This species is native to the Old World, probably to northern sub-tropical regions, but it spread widely through trade during the 20th century and is now almost cosmopolitan in distribution; it occurs throughout the Holarctic region and is established in southern temperate and sub-tropical areas, it is patchily distributed in tropical areas worldwide and, while it may not be established everywhere, there are records from most countries. Under artificial conditions it has become ubiquitous in poultry breeding establishments throughout the world and it is very probably the international trade in poultry that has caused this spread, but it has also become widely established in a variety of niches in the wild; in temperate regions it occurs in most habitats from coastal dunes to deserts, forests, grassland and urban areas, and it has adapted to living among almost any decaying organic matter including dung, carrion, farm waste and bird and mammal nests, it is also common among guano and can be abundant among accumulated bat droppings in caves. In Europe it has increased in range over recent decades and is now sporadically common throughout except in the far north, this range includes the UK where it is locally common throughout England and Wales and rather less so in Scotland and Ireland. Here it occurs in compost, dung and decaying fungi etc, and it may be abundant in poultry houses and among grain etc which has become mouldy and is attracting flies and other insects. Adults occur year-round and are active over a very long season, they fly well and so may appear suddenly in nesting material in tree hollows and roofs, and they are strongly attracted to light. The easiest way to sample them is by sieving suitable material during the spring and summer but they may occur in extraction samples throughout the year. Both adults and larvae predate eggs and larvae of other insects, particularly diptera, and in poultry houses they are considered to be a valuable control agent of diseases such as Salmonella that are carried by flies, although most such establishments carry out regular fumigation which kills the beetles as well as the flies, the flies are quick to re-establish but the beetles take longer, relying on natural populations to become introduced. However the often very
large Carcinops populations that build up will regularly disperse and re-enforce natural populations and so the beetle remains generally common. The life cycle has been intensively studied in order to assess the species’ suitability as a control agent of flies in a range of situations but mostly among manure and guano. Breeding occurs over a long season and development is rapid, which is typical for species in ephemeral habitats such as dung and carrion. Fecundity is very variable but is generally fairly low, females lay small batches of eggs among suitable host material, the frequency varies from several batches per day to a single batch every few days, this extends over a long period and the most fecund females can lay several batches of eggs each day for up to two weeks. Larvae emerge after a week or so and immediately begin to feed, they pass through two instars and are fully grown within two or three weeks depending on the availability of prey, under artificial condition they feed continuously up to a few hours before moulting, and pupate within the host material. The pupal stage lasts between two and three weeks and teneral adults occur throughout the season. Total development time from egg to adult is about six weeks although it is longer for females and dependent on temperature and nutrition; the shortest recorded was 17 days at 33°C and with unlimited food. Larvae are voracious predators that will soon reduce the population of fly larvae but adults are also valuable in this respect, they live for up to three years and have been recorded consuming thirteen fly eggs per day, they are also highly mobile and will disperse among host material or fly off to find fresh material when the local fly population becomes depleted. The problem of diptera infestations is most prevalent in warmer regions where flies can achieve super abundant levels only a few weeks after fumigation and spread to surrounding urban areas and so various parasitic wasps and beetles such as the present species are being bred commercially to help as biocontrol agents, these may also help to control other poultry house pests such as the generally abundant beetle Alphitobius diaperinus (Panzer, 1797).
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Adults are small, long-oval and convex above and below, entirely shiny black or dark reddish-brown with paler appendages. Head almost flat above, with a distinct frontoclypeal suture and complete raised border, weakly convex eyes and robust and curved mandibles. Antennae geniculate with a broad scape and pale, 4-segmented club, inserted in a short scrobe near the lower margin of the eyes. Pronotum transverse, broadest at slightly obtuse posterior angles and narrowed to forwardly-projecting anterior angles, apical margin straight, basal margin widely curved, surface evenly convex, finely punctured and with a keel along the lateral margin. Prosternum with a rounded anterior lobe projecting below the head, this is incised laterally to accommodate the antennal flagella and to ‘lock’ the large anterior tibial spur when the limbs are retracted, lateral antennal cavities more-or-less in line with the coxae, and a broad, apically curved process between the coxae. Scutellum small but evident. Elytra each with six strongly punctured striae extending almost to the apex, the first two united at the base, and a short stria above the humeral angle, interstices finely punctured throughout, in outline broadest behind the shoulder and rounded to almost truncate apical margins that leave the propygidium and pygidium exposed. Legs robust, especially the tibiae, femora broad and with tibial grooves. Middle and hind tibiae angled externally, front tibiae much broader, strongly curved internally and angled externally, the apical part with two large external teeth and a long, curved apical spur. All tarsi with five simple segments. Claws smooth and without a basal tooth.