Fam. Muscidæ (House-flies; Blow-flies).

Lucilia cæsar (Green Bottle-fly, introduced).

Abundant everywhere, living upon decaying animal matter.

Calliphora erythrocephala (introduced Blow-fly).

Abounds in all situations.

Calliphora quadrimaculata.

The common New Zealand blow-fly. Abundant throughtout the season from about September onwards.

Calliphora hortona.

Common. During October (1908) I captured a large number on Ocean Beach. On stirring up the heaps of dried seaweed which lay about the sand above high-water mark I was surprised by the large numbers of this species which emerged, together with numerous semi-transparent flies. By examining the latter I found that they were specimens of C. hortona which had evidently just completed pupation. When first obsrved, the wings were crumpled or folded up longitudinally along the margin of the dorsal surface of the abdomen. At this stage the whole body was greyish in colour, and the abdomen, when held to the light, was seen to be semitransparent. After about three hours the coloration of the mature fly began to develop: the abdomen became opaque and assumed the final blue tint, the thorax became gradually darker, the bristles took on their permanent colour, and the wings unfolded, the whole fly becoming transformed in colour. Before this transformation commenced, the ptilinum projected considerably, but was gradually withdrawn as the fly became mature. The wings of this species presented a peculiar appearance immediately after they had unfolded: two cross veins, connecting the first and second longitudinal veins, were absorbed as maturity approached. I have observed this structure in the wings of other genera.