Oryctes nasicornis (Linnaeus, 1758)
European Rhinoceros Beetle
POLYPHAGA Emery, 1886
SCARABAEOIDEA Latreille, 1802
DYNASTINAE MacLeay, 1819
Oryctes Hellwig, 1798
More generally associated with warmer regions, this group (usually quoted as a subfamily of Scarabaeidae Latreille, 1802) is represented in Europe by 5 genera and 13 species; the most widespread and familiar being the present species which occurs throughout the Palaearctic region and is represented by many subspecies, at least 11 of which occur in Europe; the nominate subspecies occurs mostly in central and northern Europe, extending into central Sweden and Finland but not the UK although a specimen was found in Chelsea in 1836 (but not recognized as such at the time) and a live female specimen was found near a moth trap in the west of England in 2013 but its origins remain a mystery. On the continent it is the only member of the family to extend into northern regions; it is locally common and can be abundant in warmer areas but in some northern areas it has been in decline over recent decades due to development and forestry management, and in a few countries it is now protected. In northern Europe adults are active from April or May, depending on the season, and they are long-lived, sometimes surviving into the autumn; they do not feed, are mostly crepuscular and nocturnal, hiding by day under loose bark or among wood debris etc although both sexes occasionally bask on trunks in hot sunshine, and they are strongly attracted to light. Mating occurs during spring and early summer when males may spend considerable time wrestling each other in the presence of females; copulation usually occurs in the evening and mated females fly off to find suitable oviposition sites. Eggs are usually laid in batches of up to fifty among decaying wood at the base of dead or dying trees but the beetles are also synanthropic and will oviposit among stored wood or even among wood debris or compost in gardens and timber mills etc. Larvae develop among moist decayed wood; they feed directly on the wood but will also consume any decaying vegetation present as well, they generally develop over two years although this may be extended to three or four years depending on temperature and nutrient availability ( in warmer areas of Asia the species may be univoltine and large populations can be damaging in orchards etc although they do not attack healthy trees), and when fully grown they form pupal cells among the wood
Oryctes nasicornis 1
Oryctes nasicornis 2
and pupate, generally late in the year. Fully grown larvae are of the typical C-shaped scarabaeiod type and may reach 100 mm when fully grown. Adults eclose during the winter but remain in situ until the temperature increases in the spring; they often emerge in numbers together and at certain times they are seen flying around lights in gardens and streets; females usually die off after ovipositing and so are rarely seen after mid-summer but males, surviving on their fat reserves, often persist until late summer or even autumn. Given the northern extent of its distribution in Europe and its lifestyle it is perhaps surprising that the species is not resident in the UK but with climate change this is probably only a matter of time.
Adults are absolutely distinctive and cannot be mistaken for any other central or northern European species (there is another member of the genus present in the western Palaearctic region, O. proxilus Wollaston, 1864, but this is endemic to the Canary Islands). They are large; 35-45 mm long, elongate, strongly convex and rich chestnut-brown in colour, the dorsal surface is glabrous and shiny while ventrally both sexes have dense yellowish-brown pubescence. Sexual dimorphism is strong; males have a long cephalic horn and several forwardly-projecting horns above an excavate anterior portion of the pronotum while females lack horns although the pronotal sculpture, while usually weak, is always evident. They are otherwise of rather typical scarabaeiod appearance with a lamellate antennal club, strongly toothed front tibiae and robust 5-segmented tarsi.