On the first Instar Larvae of some Species ofOtiorrhynchusfound on Strawberries, with Notes on their Biology

Abstract

1. There are four species ofOtiorrhynchuswhich commonly, in both the larval and the adult stage, cause damage to strawberry plants.2. The morphology of the first larval instar of these species is discussed from the point of view of their determination.3. It is shown that although the larvae in this stage are superficially very similar, there are considerable differences in the chaetotaxy of the head and also in the form of the labrum and the setae situated upon it.4. Similarly there are variations in the position and size of the setae on the dorsum of both the thorax and abdomen.5. A table is drawn up summarising all these characters in each of the four species.6. A brief description of the present knowledge of the biology of these species is also given. It appears that although all of them are usually parthenogenetic, it is at present uncertain whether they can ever reproduce sexually, since the presence of males has as yet not been recorded.7. These species usually have only one generation in the year, ovipositing in mid-summer and over-wintering as well developed larvae. In the case ofO. sulcatusandO. ovatus, however, adults may emerge late in the summer and, having hibernated as adults, lay eggs in the early spring following.