A rearing method and some biological studies of the weevil Sitona humeralis Stephens (Coleoptera: Curculionidae) in Canterbury

Abstract

A rearing method was developed to facilitate the study of the soil inhabiting stages of Sitona weevils, with particular reference to s. humeralis in Canterbury. Consideration is given to the physical requirements of both the insect and its host plant. The effects of the physical properties of soils on the physical environment in the rearing medium, are briefly discussed.

Under laboratory controlled environmental conditions, S. humeralis was reared from egg to adulthood on its host. Various aspects of preimaginal biology related to the weevil were investigated, using such reared colonies.

Using field collected adults, changes in the reproductive physiological state or the female weevil were studied over a 12 month period, during 1977 and 1978. These changes were based largely on observations from periodic dissections of the female reproductive system.

The wing condition of S. humeralis in Canterbury was also studied. In Britain, at least, S. humeralis is wing dimorphic. There is a form with fully developed wings and there is a form with much reduced wings. In Canterbury, it appears that only the fully winged form is present.