Necrobia ruficollis (Fabricius, 1775)

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POLYPHAGA Emery, 1886

CLEROIDEA Latreille, 1802

CLERIDAE Latreille, 1802

KORYNETINAE Laporte, 1836

Necrobia Olivier, 1795

Native to the Palaearctic region, this species now occurs worldwide owing to its association with stored foods and other products, it was formerly much more common but improvements in hygiene and the use of preservatives etc. in foods have greatly reduced its frequency and it is now generally sporadic and uncommon although large infestations still occur where foods are preserved without the use of chemicals. In warmer regions and under artificial conditions the species is continuously-brooded and present year-round but in natural conditions in northern temperate areas it is seasonal with adults overwintering and active from late spring until the autumn. Although much less frequent and now generally rare and sporadic the species is still recorded throughout Europe north to the UK and southern Fennoscandia; it may be imported and so occur under artificial conditions at any time, and no doubt some of these lead to populations becoming established in the wild, but it is only occasionally recorded in the wild, usually among old carrion or even on dry bones and adults sometimes appear on flowers. Adults mate soon after they emerge from overwintering and then disperse by flight to find suitable oviposition sites, they usually seek out carrion but are also attracted to stored meats and fish, especially where these have been preserved by smoking and have begun to dry out. Eggs are laid in batches among suitable host material and larvae emerge within a few days, like the adults they are mostly saprophagous but will predate insect eggs and larvae and will readily consume dead flies etc. if food becomes scarce. Larvae develop rapidly; under good conditions (optimal temperatures are 30-34°C and the minimal temperature is 22°C) the entire life cycle takes about six weeks, they passing through three or four instars before pupating later in the summer, pupation usually occurs in a silky cocoon among the host material but pupae have also been found on the ground beneath carcasses. Adults feed soon after emerging and where host material is abundant they may remain and reproduce but in the wild they will either disperse by flight or seek overwintering quarters. In the tropics they are associated with a range of stored products and are a regular pest of stored copra and some other materials, in temperate regions adults and larvae feed on dried fish, skins and bones, and have been found among decaying honeycomb and chicken waste, they have also been found in museum specimens and cadavers and are sometimes useful in forensic entomology. Sampling is usually by chance when searching carrion or stored products or when sweeping flowers but adults fly into buildings and are sometimes found on walls in food storage areas.  The species is also noted for saving the life of the great French zoologist Pierre Latreille when imprisoned and awaiting execution for refusing to swear allegiance to the state; he recognized a specimen found in his cell and passed it on via the prison doctor to the 15-year-old local naturalist Jean Baptist Bory de Saint-Vincent who, aware of Latreille’s work, managed to secure his release. Latreille had trained as a catholic priest before the revolution but the Civil Constitution of the Clergy, passed in July 1790, required the subordination of the church and for all priests to swear allegiance to the government.

Necrobia ruficollis

Necrobia ruficollis

© Lech Borowiec

A very distinctive species that may be identified by size and colour. 4.0-6.0 mm. Head black with a blue metallic lustre, antennae black, pronotum and legs orange, elytra orange across the base, otherwise dark metallic blue, entire dorsal surface with erect dark setae. Head with large convex eyes and slightly diverging temples, surface evenly convex and moderately strongly punctured, Antennae inserted laterally in front of the eyes, 11-segmented with a loose three-segmented club, Pronotum transverse, broadest about the middle and narrowed to curved anterior margin and distinct posterior angles, surface without structure, discretely punctured throughout, a little more strongly and less densely than that on the head. Elytra elongate and broadest behind the middle, with broadly-rounded shoulders and a continuously-curved apical margin, striae punctured but not impressed and tending to fade after the middle or to become lost among the background punctures. Legs long and robust, femora unarmed, tibiae narrow and tarsi extensively bilobed.