454 MAUD D. HAVILAND 
The egg is deposited in the haemocoele of the host, and in 
the course of development a pseudo-serosa or trophic membrane 
of hypertrophied cells is formed round the embryo. ‘The 
first larval stage is a transparent caudate form, which varies 
somewhat in different genera, the cauda of Aphidius being 
single, whereas, according to my observations, it is bifid in 
Ephedrus and Praon. ‘This appendage diminishes in 
the succeeding instars, and the larva, which lies curved head 
to tail in the body of the host, gradually assumes the apodous 
maggot-shaped form usual among hymenopterous larvae. At 
first the presence of the parasite makes little difference to the 
aphid, which feeds and reproduces as usual; but, as develop- 
ment proceeds, degeneration of the host’s tissues sets in. The 
embryos are affected first, and then the fat-body. The ‘ pseudo- 
vitellus ’ or symbiotic organ is not attacked until a later stage, 
and the nervous system and alimentary canal remain unchanged 
until just before the Aphidius transforms, when they, in 
common with the rest of the fluids of the body, are ingested by 
the parasite. The tissues break down into large globules, 
which in staimed preparations appear as a vacuolated mesh- 
work of connective tissue containing droplets of fat, while 
there is often a mass of degenerating nucleoplasm in the centre 
of the mass. By what means the parasite thus breaks down 
the surrounding tissues is not known, but although the larva 
possesses powerful mandibles, chemical rather than mechanical 
action seems probable. 
As soon as the Aphidius has completely emptied the body 
of the aphid, it changes apneustic for peripneustic respiration, 
and weaves a cocoon inside the dry skin with silk secreted by 
the salivary glands. 
The meconium is then voided and metamorphosis takes place. 
PAIRING. 
In Bothrioxysta curvata, reproduction was either 
sexual or parthenogenetic according to whether a male was 
introduced into the rearing-tube or not, All observed ovi- 
positions of Charips victrix took place after mating, but 
the ovipositions of Alloxysta were not determined. 
