20 
MISCELLANEOUS COTTON INSECTS. 
before April 1, the season being an exceptionally early one. The eggs 
had been laid in the hard ground on the edges of iields and in fields 
uncultivated during the present season. Young of the first instar 
taken to the laboratory on April 23 molted April 25, May 10, May 23, 
and May 30 and became adult on June 8. The habit of ascending a 
stalk of corn or weed 
during the last molts is 
illustrated in figure 9. 
It was found exceedingly 
difficult to distinguish 
the different instars by 
an}^ markings or by the 
general size of individ- 
uals, for in both these re- 
spects different individ- 
uals vary very greatly. 
It was found b} T measur- 
ing reared specimens, 
.however, that the length 
of the hind tibife was 
fairly constant for a 
given instar, and this 
proved true of a series 
subsequently measured. 
The length of the meta- 
tibia is as follows: First 
instar, 3-4 mm.; second 
instar, 5-6 mm. ; third 
instar, 8-9 mm. ; fourth 
instar, 11-12 mm.; fifth 
instar, 15-16 mm. These 
are the measurements of 
the cast skins, the meas- 
urements in the case of 
live or mounted speci- 
mens being slightly less 
in each instar. The time 
Fig. 9.— Melanoplus differentialis on corn leaves: adult ia natural of molting Varied f Ol" dif- 
position, upper figure; pupa skin below on right— n itural size f eren + individuals and 
(author's illustration). 
was governed by the 
amount of food available, so that no fixed dates can be given. In 1903, 
in a local outbreak, the first three stages, mostly the second and third, 
were found to occur on June 1. The development during these two 
seasons probably illustrates the extreme dates of earty and late develop- 
ment for this latitude. 
