Aspects of the morphology of the ovipositor of Hylotrupes bajulus (L.) (Coleoptera: cerambycidae)

Hylotrupes bajulus (L.) is a serious pest of seasoned softwoods. The female oviposits in the cracks and crevices of the wood, and the larvae can survive and feed in the wood for 2-10 years. The female H. bajulus has an elongated ovipositor comprised of the modified abdominal segments 8 and 9, intersegmental membrane 8/9, and pair of distal gonostyli. When not in use, the ovipositor is retracted within abdominal segment 7.

The 8th abdominal segment forms the proximal end of the ovipositor. An internal apodeme attached to the base of the 8th sternite allows for extension and retraction of the ovipositor. The intersegmental membrane 8/9 makes up half the length of the ovipositor. The 9th abdominal segment, along with the gonostyli, comprise the dist3 l part of the ovipositor. The 9th sternum is split along the midline to form a pair of hemisternites. The gonostyli are comprised of basal coxites and apical styli. The gonostyli are the only remnants of the appendicular oviocsitor.

Several types of sensory receptors are found on the ovipositor. Segment 8 has both long tactile hairs and short trichoid sensilla. Intersegmental membrane 8/9 has no vi sible sensory receptors. Segment 9 has campaniform receptors and short trichoid sensilla. The gonostyli have several types of sensory receptors including long tactile hairs, medium trichoid ser..silla, short trichoid sensilla, and basiconic receptors.

The long tactile hairs and campaniform receptors are innervated by a single dendri te, thus functioning as mechanoreceptors. The medium trichoid are innervated by three dendrites, two of which extend into the lumen of the receptor. The short trichoid sensilla are innervated by five sensory neurons. The basiconic receptors are innervated by 1-3 dendri tes, depending on the type and location of the receptor. All three types of sensilla function as contact chemoreceptors, and may provide information on the suitability of the oviposition substrate.