Fe D . 15, 1921 Leconte's Sawfly, an Enemy of Young Pines 753 



cuts an end completely, or nearly so, from the cocoon, and issues. It is 

 in the cocoon that this insect passes the winter. 



The length of the cocoon period, from its spinning until the issuance of 

 the adult, varies with the character of the colony. If the cocoons are 

 made by the larvae hatching from eggs laid in early summer (May or June) 

 there will be an emergence, called brood A, in the late summer or early 

 fall of the same year (late July, August, and early September) and a 

 second emergence from cocoons made by larvae of the same colony, called 

 brood B, in the late summer and early fall of the following year. In such 

 instances the length of the period between the first cococn and the first 

 adult of brood A varies from 13 to 23 days, averaging 18 days; and the 

 period between the first cocoon and the first adult of brood B varies from 

 364 to 379 days, averaging 371. 



If, however, the cocoons are made by the larvae hatching from eggs 

 laid in the late summer or early fall the emergence of brood A will not 

 take place until late spring and early summer of the following year, while 

 brood B will emerge in the late summer and early fall of the same year as 

 brood A. In this instance the time elapsing between the making of the 

 first cocoon and the first emergence of brood A varies from 205 to 242 

 days, averaging 218 days, while that between the making of the first 

 cocoon and the first emergence of brood B varies from 292 to 342 days, 

 averaging 309 days. 



The female adults seem to predominate throughout any period of 

 emergence and in a whole colony by the ratio of 3 to 1. Although the 

 females predominate for any given period of emergence or brood in the 

 sense in which it has been used in this paper, it is not unusual to find that 

 at either the beginning or end of the period males will emerge in the 

 majority. 



EFFECT OF METEOROLOGICAL CONDITIONS 



Eggs laid in late July and early August — that is, during the warmest 

 periods — hatch more quickly than those laid later or earlier in the year. 

 The particular period of the year, however, or the heat has not been 

 proved to be directly responsible for the speed of development, although 

 from temperature readings during the periods of incubation this would 

 seem to be a fact. For example, in June, 1917, when the mean tempera- 

 ture during the incubation period was 71.23 F., with a mean minimum 

 of 60. 14 , eggs hatched in 21 days; in mid-August, when the mean tem- 

 perature during incubation was 74. 59 , with a mean minimum of 63. 59°, 

 the eggs hatched in 18 days; and in late July and early August, 191 7, 

 when the mean temperature of the incubation period was 78.8 , with a 

 mean minimum of 67. 69 , eggs hatched in 13 days. 



Further, the relation of humidity to development must be considered, 

 and it would seem from our records that high humidity tends to retard 

 incubation. For example, in June, 1917, when the average humidity 

 25150°— 21 2 



