49 
ima the length of the life cycle of the insect. In the records given 
we find that tlie pcu'iods vary from 40 to about 00 days, "vvith an aver- 
age of 55 days, or about 8 weeks. Professor Gillette finds that 
according to his life history studies upon the sunmier l)rood the 
JULY AUGUST SEPT. 
IZ3A'i6 78<J I2l3'.'il6l7 8l9202l2?23a?i26272929303ll2 34'i6 7e9l0 II2I3U. Sl6 7 8 9a)2l2225»?)2627a2930i 1 2 3 4^6 78<5 Oir 20 4SX, 7!8i9202l2225a7J26772BnS 
2600 __ 
2500 1 
2400 
2300 1 1 ... 
2200 ' ^ V- -^ 
2100 1 1 ■ - ' 1 / 1 ! 
2000 . ,,, I 
1900 1 
1800 1 
1700 y 1 ' 
1600 / 1 
1500 f 
1400 
1300 
i2oo_._.Tr : 
1100 1 / 1 
1000 1 ^ I ^ 
900 1: '' M- /^^S^. , M.., 
800 ll -/■ !l| "^^^ ! 
700 M / - 1 '-< ' 
600 / ; \: / i , 1 
500 • / 1 1 iTs .'' , . '■ ; 
400 / Ss ■ ■ ." i 11 
300 / ' \ ■;' 
200 / \,'' 
100 . 
1 
Fig. 10.— Bivnd record made by David Brothers in Colorado in 1?99. 
period of the ditferent stages is as follows: From egi^ to larva, 7 
da3\s; from larva to cocoon stage, 19 days; from cocoon stage to emer- 
gence of moth, 18 daA's: from emerg^ence of moth to middle of Qgg- 
J U LY 
1 53-<.^ 678')IOlii?i3l».fii6l7SW!9?ISTOSS?7a»303l 1 ? 5 ^^ t 
AUGUST SEPT. 1 OCT. 1 
781 « 1 2i5«.is*ni9NOT23»?.Si7SBMS 1 2i*^b78<>l0 ir21J4HSi6i7l8«»2ina2i»3U7»»3l|i 2 54 S fcTa?^!!!?!^^ 
190 
180 XT. 
170 ±1 
160 T 
150 
:::::::::::::::::::::"::::::::::; i 
IM) 
130 
120 
::::::::::::::::::::::::::::::::/:: ::::: 
10 
1 I 
100 T 
:: :::::::::::::::::::+:: 1: - 
90 I 
__ / t. 
80 
70 
1 ^^ 
60 
? 
s 
50 
^/ 
40 T 
30 +\ r i^ 
20 , / 
f 
. ,,-■ 
10 - - - -\ - ? 
~.- -- ,^ 
\' 
:= t: . 
Fig. 11.— Band record publi-^^hed by rrof.C. P.Gillette, taken on 11 trees, at Fort C\>llins.Colo..in IWO. 
laying stage, 5 days (estimated): total, 49 days, or 7 weeks. From 
the writer's nunuM-ous records of tlie lengths of the ditferent stages, 
however, it is found that most iwo somewhat h)nger than those given 
6514— No. 41—08 4 
