Carpophilus dimidiatus (Fabricius, 1792)
POLYPHAGA Emery, 1886
CUCUJOIDEA Latreille, 1802
CARPOPHILINAE Erichson, 1842
Carpophilus Stephens, 1830
Probably native to Old World tropical regions, this species is now established and widespread in tropical and sub-tropical regions worldwide and is regularly imported with foodstuffs to temperate regions where it often becomes temporarily established. In Europe it is established in warmer southern regions from Portugal to Ukraine, including all the Mediterranean islands, but further north, including the UK, it is exclusively synanthropic. In the wild the species develops on over-ripe fruit or at sap runs on injured trees, but it is very versatile and during dispersal will infest any fermenting material. The species has been recorded from a very wide range of products e.g. grains, rice, pineapple, oilseed, spices, honey and fruits etc. but it depends on a fairly high moisture content and generally occurs on bulk products that have been insufficiently dried or products that have been unpacked and stored in shops or food outlets. In warmer climates the species can successfully develop in humidities in equilibrium with the natural environment e.g. in South East Asia it is sometimes a serious pest of stored rice, but as a pest it is probably most detrimental to fruit crops as it is known to spread bacteria and yeasts as well as attacking the crops directly, but in cooler climates they rely on artificial moisture. Adults are active by day and night, they are strongly attracted to volatiles from fermenting fruits and grains and can fly up to 2 miles to find suitable host material, they otherwise spend most of their time hidden among host material, often alongside their larvae. Mating occurs at any time as long as the humidity is high, and while the adults lifespan is usually four or five months, they may live for more than a year if conditions become unfavourable. Females are very fecund and each may produce more than two hundred eggs, these are laid singly on the surface of host material over a long season. Under good conditions larvae emerge after a few days and complete their development within a week or two, following a prepupal stage which may last up to a week they pupate, in the wild this occurs in the soil but in artificial conditions among the host material. Thus the cycle from egg to adult takes between 12 and 42 days, depending on conditions, and there are usually several generations each year in the wild. If the temperature falls during development both larvae and pupae are capable of entering a prolonged inactive stage in the soil, similarly adults will enter the soil to overwinter or become inactive during unfavourable conditions. Both larvae and adults feed externally among host material, they are easily spotted but both stages are agile and will move and hide quickly if disturbed or suddenly exposed to light.
2.0-3.5 mm. Elongate, broad and almost parallel-sided with short elytra which leave the abdomen substantially exposed. Dorsal surface finely punctured and pubescent throughout, body dark reddish-brown to almost black except the elytra which have a pale oblique line from the shoulder to near the apex of the suture, appendages coloured as the body or a little paler. Head strongly converging in front of round and weakly-convex eyes, surface almost flat and the anterior clypeal margin widely and rather strongly emarginate, labrum free and narrowly visible beyond the clypeus. Antennae inserted laterally in front of the eyes, 11-segmented with a compact 3-segmented club, basal segment widely expanded, segment two broader but much shorter than segment three. Pronotum transverse, near parallel-sided in the basal half to rounded posterior angles and rounded anteriorly to a curved apical margin, basal margin weakly sinuate and very finely bordered, surface moderately strongly punctured, these are mostly doubled and form an overall circular pattern except on the disc. Pronotal epipleura very finely punctured. Mesosternum convex, without a median keel. Scutellum transverse, triangular and finely punctured. Elytra transverse and curved laterally from rounded shoulders to truncate and reflexed apical margins, surface without striae, randomly punctured and with very fine granular microsculpture throughout. Pygidium and propygidium always exposed beyond the elytra. Legs short but robust, the hind femora a little wider than the others. Tibiae strongly widened from the base to truncate apices; middle and hind tibiae with two external keels and very fine apical spur. Tarsi 5-segmented, the basal segments short and broad and the terminal segment long and curved. Claws smooth and without a basal tooth.