8 Department Circular 288, U. S. Dept. of Agriculture. 



The dm'ation of the early instars has been determined rather 

 accurately, as shown in Table 2, but no individuals have been carried 

 completely through their development under close observation. 

 This has been due to the large percentage of mortality from disease, 

 especially when the larvae are kept in confinement. Development 

 is comparatively slow, and apparently 30 to 60 days are necessary 

 for growth to be completed. 



In Dallas the maximmn number of grown larvae of the first genera- 

 tion seem to occur in June and July, and of the second generation in 

 September and October. There has always been more or less over- 

 lapping of the two generations, however, and in some strains probably 



Fig. 5. — Piiss caterpillar with mosidi 111 ■ 1 ' how 



clusters of spims. 



there is but a single generation in a year. Pupation of the first 

 generation usually begins early in July and extends thi'ough the 

 month, and with some individuals much later. The duration of this 

 stage in the first or simimer generation ranges from 28 to 41 days 

 (see Table 1). The cocoons of this generation are to be found well 

 scattered over the trees, frequently being attached to the leaves but 

 more commonly to the twigs and branches. The spinning of the 

 cocoons of the second generation begins in September and extends 

 until heavy freezes occur. With this generation there is a marked 

 tendency to spin up on the larger limbs and trunks of trees, and 

 apparently a greater number leave the trees entirely and crawl 

 aoout in search of suitable places for pupation. The tendency to 

 spin up in crevices and other protected places is much more marked 

 in this than in the summer generation. The crevices in the rough 



