IOWA ACADEMY OF SCIENCES. 
213 
Later in conversation with Mr. G. W. Brown, a civil engi- 
neer of Boone, it was learned that the water was pumped into 
a large cement lined reservoir which contained the larvae in 
immense numbers and was without question the point where 
the eggs were laid, it being exposed to easy access by insects. 
It appeared also that the larvae were drained into the mains at 
times when the reservoir was low, doubtless causing strong 
currents over the bottom. Specimens have also been received 
from Des Moines. 
When mature they change to a delicate pupa (Pig. 12, A, i,) 
and then rise to the surface of the water and soon the adult 
insect escapes from a slit along the back of the pupa case. 
The adult is a delicate mosquito-like insect (Pig. 13.) belong- 
ing to the genus CMronomus but it cannot be referred to any of 
the described species and the present state of the classification 
of this genus is such as not to warrant us in giving it a scien- 
tific name or description. 
Fig. 13. (CTiironomus sp ) a, adult male, d, antenna of female. (Original). 
The insect is of interest at this time because of the great 
number of water tanks and reservoirs established, not only in 
cities and towns, but on many farms, and the probability of its 
frequent occurrence where these are open to visits of the adults. 
Exclusion of the adults, where practicable, may be accom- 
plished by the use of ordinary mosquito netting or wire gauze. 
Where this is impracticable the providing of an inlet to dis- 
tributing pipes that will draw water from a few inches above 
the bottom of the reservoir (which might further be protected 
by a fine screen) will, it is believed, avoid the distribution of 
the worms in the mains. 
