177 
LABORATORY EXPERIMENTS WITH CHINCH-BUGS. 
If the chinch-bug were practically constant in its numbers year 
after year, its regular annual appearance would be foreseen and 
might be generally provided against; but it increases and de¬ 
creases with an irregular periodicity whose causes are not yet 
fully understood, and which therefore embarrasses prediction and 
makes certain prevention impossible. It is therefore an important 
part of the problem which the injuries of this insect impose upon 
the agriculture of the State to ascertain the conditions precedent 
to its enormous outbreaks and to its almost total disappearances. 
For the purpose of getting exact information on these points I 
detailed, in July 1894, Mr. W. G. Johnson, one of the assistants 
of the State Laboratory of Natural History under my control, for 
continuous experimental investigation, to be carried on in my 
office insectary. This work was thoroughly done, under my own 
general supervision, and the results here reported are a definite 
addition to our knowledge of the habits, capacities, and relation¬ 
ships of this insect. 
The rapid increase of the chinch-bug under favorable circum¬ 
stances is of course dependent primarily on its normal breeding 
rate, but just what that rate is has not hitherto been precisely 
ascertained. It has been commonly asserted, indeed, since 1867* 
that the number of eggs deposited by a single female is about 
five hundred, but this was a mere estimate based on general field 
observations made in 1865 by Dr. Henry Shimer of Mt Carroll, 
Illinois. On this point Shimer says, “The parent chinch-bug is 
occupied about twenty days in laying her eggs, during which time 
she probably lays about five hundred eggs and then dies.” 
From Mr. Johnson’s report of the experiments above mentioned 
we learn that a single female chinch-bug kept under the most 
favorable conditions may deposit as many as two hundred and 
thirty-seven eggs, but probably few, if any, more; that the egg- 
laying period lasts about forty days, or double the number above 
given; that pairing takes place, in the summer generation, from 
four to five days after the female sheds her pupal skin; that the 
first eggs are laid in two or three days after pairing, six to eight 
days after the pupal skin is cast; that the average length of life 
of the adult female of the summer generation is about fifty days, 
and that of the male about seventy-eight days; that the female 
pairs very frequently, perhaps every day, during the egg-laying 
* Proc. Acad. Nat. Scl. Phil., 1S67, p. 79. 
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