THE HyMENoPTERA OF MINNESOTA 165 
There are over 1,200 species of the suborder in Great Britain 
alone, and probably more than 6,000 described species. Unquestion- 
ably, there are more species still unknown. ‘The tropics, for example, 
offer a field practically unworked. 
The larvae are all 
parasitic, principally 
on caterpillars, de- 
stroying enor- 
mous numbers of 
these pests. Some 
attack spiders. 
Attacks by these 
parasites are not con- 
fined to land species, 
for one [European 
form, Agriotypus ar- 
matus, 1s aquatic, go- 
ing under the water 
and remaining there 
for a considerable 
period in order to lay 
lig. 41. Cocoons of a Vipionid Apanteles (Pro- . 
topanteles) congregatus, Say on Young Tobacco Worm. its eggs on larvae of 
Natural size.—Courtesy of the Conn. Ag. Exp. Sta. anys 
caddis flies. 
A single genus, Aphidius, contains parasites on plum louse, cur- 
rant, rose and wheat lice, as well as lice infesting cherry, willow, pop- 
lar and cabbage. 
Breathing in the larval stage is effected by osmosis between the 
body of the parasite and the lymph or blood of its host in which it lies. 
VIPIONIDAE 
Cutting edge of mandibles turned inward, their tip meeting or overlapping, when 
the mandibles are flexed toward the mouth ; mesothorax with its sternum and pleurae, 
or at least the latter, not divided into an anterior and posterior portion by the 
presence of a carina or suture, in short, without a prepectus; second and third ter- 
gites fused as is evidenced by the apparent second tergite having two pairs of spira 
cles. 
Found in willow galls; parasitic on some hairy caterpillars, cot- 
tony maple scale, etc. 
Neopius carinaticeps Gahan has been reared from Agromyza 
mines in Hordeum. Ofius (Eutrichopsis) dinidiatus Ashm. is a 
parasite of Agromyza pusilla, and O. foveolatus Ashm. parasitizes 
Pegomyia. 
