Gibbium psylloides (de Czenpinski, 1778)
Shiny Spider Beetle
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POLYPHAGA Emery, 1886
BOSTRICHOIDEA Latreille, 1802
PTININAE Latreille, 1802
GIBBIINI Jacquelin du Val, 1860
GIBBIUM Scopoli, 1777
Although widespread in Europe and sometimes locally common e.g. throughout much of France, this species is only rarely recorded in Britain; there are a few records scattered throughout England and Wales north to the Scottish borders. Here it is synanthropic, inhabiting stores, houses and warehouses etc. but on the continent it also occurs in attics, barns, shed and out-houses as well as food storage areas. The adults are strongly photophobic, move slowly and generally inhabit shady and damp places, they are cool tolerant and long-lived; generally around a year but individuals have been kept in culture for up to 18 months and they can survive for long periods without food. They develop on a wide range of foodstuffs of both plant and animal origin and have been recorded damaging books, fabrics and museum exhibits although they are usually considered a nuisance rather than a pest. In temperate regions mating occurs in the spring and the females are very fecund, laying up to 500 eggs, usually in late spring or summer and so large infestations are not uncommon. The eggs are laid among suitable plant or animal debris in secluded situations and they hatch within 2 weeks, the larvae develop rapidly and are fully grown within 6 weeks; when mature they are up to 4mm long, soft-bodied and pink or grey with a dark head, and covered with erect pale yellow setae. Pupation occurs in a cocoon among or near the food and this stage takes 3 or 4 weeks to complete, the eclosed adults remain within the cocoon maturing for a week or so before emerging. Under optimum conditions, about 33°C and 60% R.H, the life cycle takes between 60 and 70 days and there may be 3 or 4 generations in a year.
1.7-3.2mm. entirely reddish-brown or with the foreparts darker and the appendages lighter, upper surface shiny and appearing glabrous, elytra very convex above and below; globose and widest behind the middle. In side view the head, pronotum and elytra contribute to a single curve. Head small and transverse from above, flat anteriorly and with rather dense very fine pubescence, especially between the eyes and the antennae. Eyes circular or nearly so; small and rather flat. Antennae long and robust, covered with dense fine golden pubescence, their insertions close together in front of and below the eyes. Genae with long and apically dilated setae (X100), lateral furrows distinct but sparse on the top of the head and not confluent. Pronotum transverse and highly arched, without borders and produced back medially at the base. Scutellum tiny or hidden beneath the produced pronotum. Elytra quite smooth, without striae but sometimes longitudinally wrinkled around the base. Legs robust, long and completely covered with dense pale setae; femora strongly expanded from about halfway to the apex, tibiae flat and gradually dilated towards the apex, the lateral margins being strongly sinuate on the hind tibiae. All tibiae produced apically into a lateral spur; the front pair externally, and the mid- and hind pair internally, Tarsi 5, 5, 5, without lobed segments, claws simple.
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Gibbium Scopoli, 1777
This is a small genus of 3 very distinctive species of tiny mite-like beetles that occur among plant and animal products and debris in warehouses and stores etc. All occur in Europe and at least 2 are native to the Palaearctic region but they are now much more widespread due to trade, and in warmer climates they also occur in the wild. They are quite unlike any other species and distinct due to the very convex and shiny elytra and the more-or-less continuous body outline; a narrow head and a pronotum gradually widened from the front angles to the base where it is as wide as the elytra. All species are small, ranging from 1 to 3.3mm, and apteruos with fused elytra and long appendages. They are drab coloured, from pale brown to almost black, often with the appendages lighter. The dorsal surface appears glabrous although they are very finely and diffusely punctured and pubescent. The head is flat anteriorly with small, weakly convex eyes and dense transverse furrows laterally which generally extend up and behind the eyes, the antennae are 11-segmented and filiform, without modified segments, and placed very close together in front of and below the eyes. The scutellum is usually indistinct and the legs are very long, distinctly shaped and densely pubescent. They display no obvious sexual dimorphism.
The species are:
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G. psylloides (Czempinski, 1778). Widespread Palaearctic, South-East Asia and North Africa.
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G. aequinoctiale Boieldieu, 1854. Almost cosmopolitan with most records from tropical or sub-tropical areas, widespread but very local in Europe.
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G. boieldieu Levrat, 1875. A very local species in Europe, Caucasus and South-East Asia.