14 ; DEPARTMENT BULLETIN 179. 
Similar results were obtained as a result of life-history experi- 
ments during 1915. 
The death rate of nymphs under observation in the laboratory 
was very high and increased the difficulty in obtaining data on the 
length of the different stages, but it is believed that the durations of 
the instars given above coincide very closely with the actual periods 
occupied by the nymphs in the field. 
DETAILS OF MOLTING. 
When the nymph is preparing to molt it generally assumes a posi- 
tion with the head downward. After a quiescent period varying 
from 15 to 50 minutes the process of molting begins. The thorax first 
splits down the median dorsal line, then the integument connecting 
the dorsal plates of the head and thorax splits transversely, allowing 
~ the head to fall forward. The thoracic region now becomes elevated, 
as a result of pressure exerted from within, and the split in the molt- 
ing skin more pronounced. This causes a transverse separation of 
the integument connecting the dorsal plates of the thorax and abdo- 
men to a point nearly as far as the lateral edges of the dorsal thoracic 
sclerites. The molting nymph first extracts the head and its ap- 
pendages and then the first, second, and third pairs of legs. As soon 
as the legs are free they are used as a lever in extracting the remainder 
of the thorax and abdomen from the molted skin. In four instances 
under observation the process of molting required from 9 to 12 
minutes. 
The newly molted nymph appears to be prepared to resume its ac- 
tivities within a few moments after the completion of its molt. 
With the exception of the ruptures noted above, the cast nymphal 
skin remains intact and greatly resembles a ving nymph. 
RELATION OF TEMPERATURE TO NYMPHAL DEVELOPMENT. 
In order to determine the relation of temperature to nymphal de- 
velopment an equal number of nymphs hatching at the same time 
from the same egg cluster were kept under maximum daily tempera- 
tures of 70° and 90° F., respectively. The nymphs developing under 
the lower temperature required an average of 5 days longer for the 
first instar and 7 days longer for the second instar. (See Table L.) 
It is evident that cool weather retards nymphal development to a 
marked degree. 
ADULTS. 
PERIOD BETWEEN MATURITY AND BEGINNING OF OVIPOSITION. 
The ovaries of newly matured females do not contain eggs. Ina 
series of laboratory experiments wherein pairs of reared adults were 
confined in individual cages, the minimum period between maturity 
— 
