IIYMENOPTEHA. 
125 
that of a small artichoke, etc. etc., one cannot say. 
The problem still remains to puzzle us. 
The Naturalist after collecting a number of galls, 
for the purpose of discovering the various kinds of 
Gall-fly inhabited by them, cannot be sure that the 
little insect he sees to emerge from its place of conceal¬ 
ment, is the original and lawful occupant, for there are 
various kinds of Ichneumon flies, which in their turn 
pierce the body of the young Gall-grub wherein they 
deposit an egg, from which is produced a parasitic 
Ichneumon, which feeds on the young Gall-grub, and 
eventually comes forth from the same hiding place. 
The Gall-flies are small insects, the largest species 
known in England being the Cynips Kollari , already 
noticed. 
I ought to notice that both in the Saw-flies and the 
Gall-flies the males seem very rare. Mr. F. Smith once 
collected about a bushel-and-a-half of the galls of C. 
Kollari , for the purpose of finding a male. None but 
females made their appearance. Yet when he placed 
the female flies in various places, on oak trees, and 
visited them afterwards he found new galls on those 
' 
trees, but on no others in the neighbourhood. Here is 
an instance of parthenogenesis, evidence of the existence 
of which in the Cynipidse has lately been commented 
upon by Siebold, who has also considered the fact of 
the rarity of the male. Many species of the Tenthredinse 
(Saw-flies) exhibit the same phenomenon. 
The Evaniidce are most extraordinary looking 
insects; the family contains only a few species, which 
are parasites on cock-roaches (Blattre). Evania ap - 
pendigaster has an enormously developed thorax, and 
