The life history and morphology of the early stages of the yew gall midgeTaxomyia taxi(Inchbald) (Diptera: Cecidomyiidae)

Abstract

Summary 1. The majority of individuals of Taxomyia taxi develop in two years and these induce the formation of artichoke galls on yew Taxus baccata in their second year. A small number (usually <10%) mature in one year and inhabit galls which never develop further than swollen buds. The life cycle rarely (<2%) takes longer than two years. 2. Eggs are laid in early June, they hatch in one to three weeks and galls are formed in dormant buds which would produce the following year's leaf shoots. There are three larval instars between late June and mid-April of the following year (one-year life cycle) and mid-April of the next year (two-year life cycle); the pupal stage lasts six weeks and adults emerge in late May and early June. 3. The rate of development of the first instar differs in the two life cycles: about fourteen months in two-year and two months in one-year galls. After instar I, development is identical. 4. Larval weight increases most rapidly during instar II, just after eruption of the meristem i...