f 
2 BULLETIN 1008, U. S. DEPARTMENT OF AGRICULTURE. 
in recent times. In 1861 Wagner? by confining a female Hessian fly 
with wheat plants secured a total of 83 eggs. He evidently carried 
out other experiments, for he concludes that the number of eggs de- 
posited by a female is more than 80 and less than 100. Koeppen ® in 
1889 stated that, according to Lindemann, a female may deposit up 
to 200 eggs, but believed these figures too high and gave Haberlandt’s 
statement that the female deposits only from 40 to 50 eggs. 
The most careful observations up to the present time seem to be 
those made by Enock.* He confined the female insects in cages with 
barley plants, securing in one case a maximum of 158 eggs. He also 
confined females singly in corked vials and secured in this way a 
maximum of 130 eggs. The number of eggs he secured by these 
methods ranged from 70 to 158, with an average for 10 cases of 113 
eggs. He concludes that a Eaele female lays from 100 to 150 eggs. 
Although Lugger® dissected a female which contained 238 eggs, the 
usual figures given since the date of the paper by Enock are based 
on Enock’s conclusion. This conclusion, however, resulted from an 
insufficient number of experiments, and the methods used in obtaining 
the counts will not give accurate results. The adults of the Hessian 
fly are extremely sensitive to conditions of temperature and moisture. 
The females normally oviposit at comparatively low temperatures and 
when moisture in abundance is present. If these conditions are ~ 
reversed or if conditions are unsatisfactory in some other respect, 
the females will die before depositing all their eggs. A new and 
thorough study of the subject therefore seemed imperative. 
METHODS OF. INVESTIGATION. 
For the reasons stated, the method of confining female Hessian _ 
flies in vials and all other methods imvolving their confinement in 
cages kept in the laboratory were rejected. Cages kept outdoors 
at the usual times when adults are abroad were piss dispensed with, 
because any cage modifies natural conditions, more or less, and be- 
cause it is difficult to secure accurate counts where eggs are scat-- 
tered over a number of plants. 
The writer is convinced that under normal conditions each female 
deposits practically all of her eggs. It has been found that at the 
.time of eclosion each female contains her normal allotment of eggs 
in a well-developed condition; in fact, it is possible to count all of 
the eggs by dissecting the pupa stage. It seemed simpler and more 
2 WAGNER, BALTHASAR. OBSERVATIONS ON THE NEW GALL-GNAT. Fulda, 1861. Trans- 
lated in U. S. Entomological Commission, Third Report. Appendix II, B, 1883, p. [15]. 
3KoEPPEN, F. T. Dip SCHAEDLICHEN INSEKTEN RUSSLANDS. St. Petersburg, 1880. 
Translated in U. S. Entomological Commission, Third Report, Appendix IV, 1883, p. [41]. 
*Enock, F. THE LIFE-HISTORY OF THE HESSIAN FLY, CECIDOMYIA Se Say. - 
In Trans. Ent. Soc. London, p. 332, 1891. 
5 LuGcer, O. THE HESSIAN FLty. In Minn. Agr. Exp. Sta. Bul. 64, p. 552, 1899. 
