6 INSECTS INJURIOUS IN 1902. 
APPEARANCE AND LIFE HISTORY OF THE HESSIAN FLY. 
The fly is dark colored, much smaller than an average sized 
mosquito which it somewhat resembles. Each female lays on an 
average over 200 eggs (generally early in May in this latitude) 
on the upper surface, usually, of the leaves of the wheat. It is 
known to also infest to a slight extent barley and rye but I have 
found its presence hardly appreciable in barley in Minnesota. 
The eggs are reddish, very small and hatch in about four days, 
the maggots crawling down the leaf until they get between the 
leaf and stalk where they feed upon the latter. After a few weeks 
Fig. 4.—Female of Merisus destructor Say. Enlarged. Lugger. 
each maggot changes into the so-called “flax seed.” In this stage, 
in Minnesota, the insect passes the winter and emerges as a fly in 
the spring. To the best of our knowledge there is but one brood 
in this state though this question is a problem the entomologist 
has promised himself to endeavor to solve next season.* Ex- 
cessive dryness and heat during the “flax seed” stage is highly in- 
jurious, the development being aided by dampness, this pest thus 
radically differing from the Chinch Bug. 
At least seven parasites are found in America affecting this 
pest; about as many in Russia and ten are quoted in England. 
The principal parasite is a minute four winged fly Merisus de- 
*Since writing the above I have been creditably informed that “flax 
seeds’ were found in abundance on wheat five inches high in the latter 
part of last June on the farm of C. Johnson, near Warren, Marshall 
county. 
