104 MAUD D. HAVILAND 
been recently hyperparasitised by Ly gocerus cameroni. 
Hence, within certain limits, this species seems to be poly- 
phagous. 
MATERIAL. 
The material used was obtained in Cambridge in the summer 
of 1919. At the end of June,a variety of L. testaceimanus, 
Kieff., was reared from the larvae of Aphidius salicis, 
Hal., parasitic in the sexuales of Aphis saliceti, Kalt.,on 
the willow ; and as the host material became scarce, I subse- 
quently induced it to oviposit on larvae of Aphidius ervi, 
Hal.,in Macrosiphum urticae, Kalt., onthe nettle. In 
July, I reared a number of L. cameroni, Kieff., from the 
latter material collected round Newnham ;*and as the host was 
plentiful, and, owing to its larger size, easier of dissection than 
the parasites from the willow, I worked with it exclusively in 
July and August. The followmg account therefore applies 
especially to L. cameroni, though the life-history of 
L.testaceimanus is essentially the same. 
Aphides parasitised by A. ervi were collected in the field, 
but a proportion of these were found to be already hyperpara- 
sitised by certain Chalcidae and Cynipidae. To ensure a * pure 
culture’ of Lygocerus, nettles infested with Macrosi- 
phum urticae were placed in water under bell-jars in the 
open air insectary, and exposed to Aphidius ervi. The 
aphides were kept under cover during the development of the 
parasite, and when the latter were about to transform, the 
leaf was cut off, and placed in a glass tube with a fertilized 
female of Ly gocerus. Thus the possibility of an infection 
by another hyperparasite was virtually eliminated. 
I tried many times to cut open a flap on the dorsal side of the 
aphis skin, hoping by this means to follow the complete develop- 
ment of the hyperparasite from day to day. but the attempt 
always failed through the death of both the Aphidius and 
the Proctotrypid within a few hours. 
