396 Phylum Arthropoda 



maintain the original volume. By these means the conditions of a semi- 

 stagnant pool were simulated. By screening the pans, several generations 

 of bloodworms were raised in the same pan.* 



In the outdoor experiments, a sluice of about 125 ft. x 3 ft. and also 

 a series of three ponds fed by pipes from this sluice were constructed. 

 This sluice and the ponds, having been artificially stocked, received milk 

 waste daily. Other forms naturally found their way into these artificial 

 breeding places but Chironomus cristatus easily maintained itself as the 

 dominant form present. 



During the 1st instar a thousand larvae will not take care of more 

 than 0.1 cc. or 2 drops of milk waste in 300 cc. of water each day. 

 They will, however, thrive in this medium and keep the water clear and 

 odorless. The length of this instar varies with temperature but around 

 65 ° F. it is normal to look for the molt about the eighth day. During 

 the 2nd instar, which lasts about 7 days, the food percentage may be 

 raised to 0.2 cc. per 300 cc. of water for a thousand larvae. The 3rd 

 instar lasts about n- 18 days and during this stage the food percentage 

 may be raised to 0.5 cc. per 300 cc. for a thousand larvae. This is also 

 the best growing medium for a mixed lot of larvae of all ages. The 

 duration of the 4th instar is extremely variable and during this stage the 

 same food percentage is used as for the 3rd instar, though a higher one 

 may be used for several days without detriment. 



The pupal stage seldom lasts more than 3 days and the adult life is 

 about 4 or 5 days. 



M. E. D. 



Reference 

 For the rearing of midge larvae see also p. 392. 



Family cecidomyidae 



A METHOD FOR STUDYING THE HESSIAN FLY 

 AND OTHER INSECTS** 



IN THE Hessian fly investigations, the wheat was planted in soil or 

 sand and allowed to grow to a height of two or three inches. The 

 plants were then removed from the soil, the roots thoroughly washed to 



♦Editor's Note: In Canad. Ent. 49:418, 191 7, Chi Ping, of Cornell University, re- 

 ported the rearing of C. riparius and C. decorus larvae on ground leaves of Potamogeton 

 and on leaves and stems of Elodea. He kept imagines in the laboratory in bell jars near 

 a window where they were exposed to sunlight for only several hours during the day. 

 Moisture was maintained to saturation by keeping Elodea and Sphagnum in the jars, by 

 sticking a few pieces of fully saturated blotting paper to the inner surface of the glass, and 

 by wetting the cheesecloth that covered the top. M. E. D. 



** Abstracted from an article in Ann. Ent. Soc. Amer. 14:227, 1921, by the late James 

 W. McColloch, Kansas State Agricultural Experiment Station. 



