446 
The Prcgress of the Hessian Fly. 
but that the species differ in each country, as shown by the 
following Table * : — 
Larvje are infested in America ty : — 
^lerisns destructor. Say. 
Merisus subapterus. Riley, 
Tetrastichus productus. Eiley. 
Eupelmus alynii. French. 
Platygaster Herrickii. Packard. 
LarvK are infested in Piussia by : — 
Merisus intermedins. Lindeman. 
Tetrastichus Piileyl. Lindeman. 
Eupelmus Koeschii. Lindeman. 
Platygaster minutus. Lindeman. 
Semiotellus nigripes. Lindeman. 
Euryscapus saltator. Lindeman. 
Platygaster (?) 
It remains a moot point, then, as to whether the parasites 
of the Hessian Fly in Great Britain are of American or Russian 
origin. This will probably soon be cleared up. That there 
are parasites present, and that they destroy the Hessian Fly 
is perfectly clear, and there is every reason to believe that they 
will be as useful in checking its increase as in America. As 
far back as 1841 Herrick stated that a very large proportion, 
probably more than nine-tenths, of every generation of the 
Hessian Fly is destroyed by parasites.! Packard quotes a 
statement to the effect that " the Hessian Fly was nearly exter- 
minated in Kalamazoo county by the Semiotellus (^Merisus) 
destructor (Say), nearly all the ' flax-seeds ' having been de- 
stroyed by the friendly parasite." % This appears to be the 
most destructive of all the American parasites, and as it is 
much like the Russian species, Merisus ivtermedius (Lindeman), 
found in Great Britain, both in appearance and in its habits, 
it is desirable to give its modus operandi as described by Pro- 
fessor Riley. He savs that the " eggs of this parasite are without 
much doubt deposited in the hall-grown larvae of the Hessian 
Fly early in the spring, and in the more southern portions of 
the wheat belt there are, in all probability, two generations, 
the first issuing from the puparium in April and MaVf and the 
second issuing all through the summer and fall. jNIany, judging 
irom my own experience in-doors, hibernate in the pupa state 
within the Cecidomyid puparium, and cut their way out in 
the following spring. In the north, however, there seems to 
be but one generation." § 
Semiotellus [Merisus') destructor, as shown at Fig. I. on p. 447, is 
only about the eighth part of an inch long, with a wing expanse 
• ' Die Pteromalinen der Hcsscn Fliege.' Von Prof. K. Lindeman. 
t ' A brief preliminary note of the Hessian Fly and its Parasites,' by Edward 
C. Hirrick. American Journal of Arts. 184L 
t Op. cit. 
§ 'On the Parasites of the Hessian Fly," by C. V. Riley. PrMetdings of 
United States National Museum, vol. No. 2t. lSt>5. 
