29 
spot appeared 2 to 3 da\'s later. This shorter averao-(! may ))e 
account(;d for by the fact that these eg^'s were kept at a higher tem- 
perature than normal. 
METHODS OF OBTAINING EGGS. 
There arc two ways of obtaining eggs for .study. The first is to 
collect them in the field and place them under observation in cages. 
There is a serious objection to this method, as there is no way of 
knowing the age of the eggs. The second method, that of confining 
larva3 and pup« and allowing the moths to emerge, is far moi'e satis- 
factor}- . If these moths are placed in a cage over a limb of a tree, 
one will find eggs in abundance in a day or two. One is sometimes 
fortunate enough to find moths in copula, and in that event they 
should be placed in a separate cage. B}^ determination of sex of the 
various moths nuich more vahiable data can be secured. Care must 
be taken that too many eggs are not laid in one cage, as in that event 
it is difficult to keep accurate notes. 
These limb cages are bags made of mosquito netting of finer mesh 
than the ordinary netting. By this method the leaves and fruit are 
alwavs fresh and the conditions are exactlv the same as in the orchard. 
INFLUENCE OF TEMPERATURE UPON THE LENGTH OF THE EGG STAGE. 
It has often been stated that a higher temperature caused the eggs 
to hatch in a shorter time, but onl}^ a few definite observations have 
been recorded. The temperature used in these calculations is the 
effective temperature, which is obtained by subtracting 43" from the 
mean daily temperature as recorded by the United States Weather 
Bureau station at Boise, Idaho. 
Professor Gillette gives 6^ daj^s as the length of this stage at a tem- 
perature of from 68° to 70° F. and 6 days as the time in a greenhouse 
where the temperature was 110° F. at midday. In Table I the total 
and average effective temperature is given from the time the eggs 
were laid until they were hatched. These data are arranged accord- 
ing to the temperature in Table II. 
Tahlk TI. — -Kfective teiiipenfturc ((ud jxriod of iiicuJxttio)). 
Average 
Total 
Average 
Total 
Average 
Total 
effective 
effective 
Length 
eflfective 
eflfective 
Length 
eflfective 
eflfective 
Length 
temper- 
temper- 
of stage. 
temper- 
temper- 
of stage. 
temper- 
temper- 
of stage. 
ature. 
ature. 
ature. 
ature. 
ature. 
ature. 
or. 
° F. 
Bays. 
°F. 
° F. 
Days. 
°F. 
OR 
nays. 
12 
298 
24 
24 
217 
9 
25 
2M 
10 
18 
216 
12 
24 
269 
11 
•JSO 
11 
19 
228 
12 
24 
295 
12 
■2~ 
307 
10 
19 
253 
13 
24 
349 
14 
•_>7 
3(56 
12 
22 
247 
11 
24 
364 
15 
2i) 
269 
9 
22 
260 
12 
24 
428 
18 
30 
278 
9 
23 
206 
9 
24 
428 
18 
47 
285 
o ' 
23 
276 
12 
25 
247 
14 
Average total effective temperature, 302° K 
