THE TERRAPIN SCALE. 57 



trades more and more through this slit and the head is forced down- 

 ward. Before the head escapes the anterior legs are withdrawn from 

 their sheaths. These are the first appendages to become free. They 

 push the case downward until the head is free. After this they force 

 the case backward under the body. The antennal sheaths cling 

 tightly to the antennae and have to be stripped free from them. The 

 middle and posterior legs take no active part in the molt, but lie 

 motionless along the edges of the abdomen. The antennal sheaths 

 are the last parts of the case to be shed. After the head escapes from 

 the case it presses against the anterior end of the puparium, which 

 serves as a fulcrum in forcing the adult free from the pupa case. 

 Pupae that escape by accident or are removed from under the pupa- 

 rium are unable to complete the molt. They continue the effort for 

 about 24 hours and then die. In the case of weak specimens the 

 impulse to molt often ceases before the tips of the antennae are free. 

 After this molt the pupal case is usually found lightly clamped under 

 the posterior edge of the puparium. (See PI. 11,/.) 



This molt ordinarily requires about 2 minutes for specimens at 

 temperatures above 70° F., but at a temperature of 66° F. the time 

 required is 5 minutes. This molt should take place about the forty- 

 seventh day, but it is frequently delayed. For example, part of a 

 brood that' emerged August 9, 1912, was removed from the trees 

 when in pupa. They were placed in the laboratory late in September, 

 away from heat and sunlight, and under these conditions many of 

 the specimens died. The remainder were abnormal and did not molt 

 until the fifty-fifth day, or 8 days after the natural time. It was evi- 

 dent that a slightly longer delay would have resulted in the death 

 of all the specimens in the pupa or during the molt. 



The Adult Male. 



The fourth molt, like the third, is made under the puparium. The 

 young imago at first has soft and folded wings, but these soon assume 

 their natural shape. Several hours, however, are required for them to 

 harden and to become fully colored. After expanding they protrude 

 slightly from under the posterior end of the puparium and serve as a 

 means of identifying this stage. The time spent under the puparium 

 varies from a few hours to 4 days. The normal time for the male to 

 remain under the puparium is from 1 to 2 days. The male regularly 

 enters the imago in the forenoon of one day and emerges during the 

 afternoon of the following day, but there are well-defined exceptions 

 to this. If favorable weather has so accelerated the growth as to 

 shorten the preceding instars, the imago tends to remain under the 

 puparium until the regular time for emerging, but when the early 

 instars are lengthened by unfavorable weather the imago emerges in 

 less than 2 days. 



