NESTING-BEHAVIOR, ONTOGENY AND LIFE-CYCLE OF ONTHOPHAGUS-STYLOCERUS (COLEOPTERA, SCARABAEIDAE)

Reproductive biology, nesting and ontogenetic development of Onthophag us stylocerus Graells, 1851 are studied under laboratory conditions. T he species is univoltine. Egg-laying begins at the end of May and last s until July. The development from oviposition to image takes 7-10 wee ks. The aestivation of the offspring is combined with hibernation of e mergent adults. As with many other Onthophagini, sexual cooperation an d food relocation for larval supply plays an important role in the nes ting behaviour of O. stylocerus. Nest type may follow any of four patt erns, involving: one or more entrance tunnels, branching and brood mas s location. Pattern 1: simple, without branching; 1 to 5 brood-masses per nest; moderate depth: 60-160 mm. Pattern 2: simple, with branching but without brood masses in the stretch closest to the surface; 3-9 b rood masses;depth: 100-315 mm. Pattern 3: simple, with branching, and brood masses in the stretch of tunnel closest to the surface; 6-7 broo d masses; depth 130-220 mm, frequently 200-220 mm. Pattern 4: complex, with one or several entrance tunnels intersecting the main shaft at d ifferent levels or converging from the surface to the same brood mass; 10-14 brood masses; depth 280 mm.Early spring emergence of O. styloce rus gives the larvae the time necessary to complete their development before the arrival of the Mediterranean mountain winter, and enables a dults to avoid the severe competition which structures coprophagous co mmunities in the late spring.