84 THE ENTOMOLOGIST. 
With us it is rare; on June 7th, 1899, Tutt sent me two live 
examples, which had just emerged from an unknown Lepi- 
dopteron near London ; and at the end of the following June 
I received another, taken by Dr. R. T. Cassal at Ashby, near 
Doncaster. The only other species is P. tricolor, Wesm., found 
in Belgium, France, and Germany; both species have been 
raised from Cochlidion limacodes, Hufn. 
HeTEROGAMUS DISPAR, Curt. 
Distinctly infrequent, though commoner than the last in 
northern Europe, extending to Helsingborg in Sweden. The 
tricoloured antenne of the 2 are distinctive, and its much 
narrower form will distinguish the ¢ from similar pale forms of 
Aleiodes. Bignell found it in Devon, Marshall at Botusfleming 
in Cornwall, Cornworthy in Devon, and Charlton in Wilts; and 
Bridgman says (Tr. Norf. Nat. Soc., v, p. 68) that he swept two 
? 2 from a lane bank on July 29th, 1889, at Earlham, near 
Norwich. Piffard has given me the female from Felden, near 
Boxmoor, in Herts; and I believe the species to be nocturnal, 
like so many other testaceous Hymenoptera, because I have 
swept it (from heather) at Butts Lawn, near Lyndhurst, at dusk 
on August 6th, 1901, and also, in the pitch dark, long after dusk, 
in Herringswell Fen, Suffolk, on August 21st, 1905. It has not 
yet been bred, though some connection with larches is suggested. 
Ruoaas, Nees. 
The species of this genus, and perhaps of the whole tribe, are 
remarkable and unique among parasitic Hymenoptera in that 
they slay their host when it has lived long enough for them 
themselves to attain the full-fed condition. Thus quite small 
Poplar Hawk larve are found dead, which in other circumstances 
would have attained the pupal state when attacked by the largest 
Ichneumon. In every instance the host remains attached to the 
food-plant; its skin hardens and protects the enclosed Rhogas, 
which in my own experience is always a solitary parasite. The 
distortion of the host’s skin during induration renders post 
mortem determination impossible. Marshall’s tables of the 
species of this genus were founded far too much upon mere 
coloration, and he himself owns the difficulty of seizing constant 
characters to distinguish insects, so variable in this very respect. 
In 1892 Prof. C. G. Thomson, of Lund, published (‘ Opuse. Ent.’ 
xvi, pp. 1659-82) an excellent account of such species as were 
known to him; and with this I have attempted to amalgamate 
the remainder of the palwarctic kinds, by no means an easy task, 
because the divisional characters employed by him had not 
previously been noticed in descriptions. 
