FNZ 39 - Molytini (Insecta: Coleoptera: Curculionidae: Molytinae) - Life History and Biology
Craw, RC 1999. Molytini (Insecta: Coleoptera: Curculionidae: Molytinae). Fauna of New Zealand 39, 68 pages.
( ISSN 0111-5383 (print), ; no. 39. ISBN 0-478-09325-X (print), ). Published 4 Feb 1999
Life History and Biology
Larvae of Lyperobius and of two Hadramphus species (H. spinipennis, H. tuberculatus) feed on herbaceous perennial Apiaceae in the predominantly New Zealand genera Aciphylla and Anisotome. Fouveaux Strait to Snares popu-lations of the southern species H. stilbocarpae are found on the fleshy herb Stilbocarpa (Araliaceae), but south-west Fiordland populations use Anisotome lyallii as a host.
Larvae are found both in the thick main roots and rhizomes of the host plants (Bull 1967, May 1971, 1981) and in soil surrounding the roots (Bull 1967). Larvae of L. hudsoni and L. montanus have also been found grazing on leaf bases and crowns. L. huttoni larvae construct a bare pupal chamber in the soil adjacent to the roots of the host plant. The pupal stage lasts about 2 weeks. After eclosion the teneral adults remain in the chamber for almost 8 months before emerging. The lifespan of adult L. huttoni in the wild has been estimated at 2.5 years (Bull 1967).
Larvae of H. pittospori are subcortical borers in the live branches, trunks and root crowns of the woody host plant karo (Pittosporum crassifolium). Their egg-shaped pupal chambers are found in the centre of the workings. The pupal stage lasts about 3 weeks. Adults of this species have remained alive in captivity for 3 years (Bennett 1987).
Hadramphus adults are nocturnal, whereas those of Lyperobius are diurnal, feeding actively on leaf tissue, flower stems, and developing seeds (Barratt 1985, Bennett 1987, Bull 1967, Meads 1990). Adult L. huttoni employ two types of feeding - leaf nicking on the outer leaflets of the host, and a deep ovoid notching of the leaf petioles (Bull 1967). Kuschel (1971: 242) described feeding behaviour of H. stilbocarpae as "adults notch leaf margins at night." D.S. Horning (in litt.), who observed this species in the field, notes: "We saw many weevils feeding on Stilbocarpa and not one of them was notching the leaf margin. Rather, they fed on the leaf by chewing a hole through it and then enlarging the hole. Often this is close to the leaf margin and the narrow strip between the edge of the feeding hole and the leaf margin may break, creating an illusion that the leaf margin has been notched." Meads' (1990: 49) photograph of this species feeding confirms Horning's account. Adults of this species can congregate in large numbers on a single host plant and feed until it dies (Close 1997).