37O J. T. PATTERSON. 



larvae. Dissections of a large number of infected caterpillars, 

 twelve to fifteen days old, reveal the presence of asexual larvae 

 in nearly every case. It is probable that in a few cases no 

 asexual larvae are developed. It is also difficult to determine the 

 exact number of asexual larvae produced by a given egg. This is 

 due to the fact that these larvae are formed continuously from ths 

 third to the fifteenth day, and those first developed degenerate 

 before the last ones appear. The smallest number of larvae 

 found was one, the largest fifteen. Careful dissections of a 

 series of infected caterpillars reared in the laboratory gave the 

 following data on asexual embryos and larvae: 



Ser. 251, a. Twelve days old 6 free larvae; 5 embryos. 



Ser. 252, a. Fourteen " " i degenerating larva; i embryo. 



Ser. 274, j, 5 free larvae; 5 embryos. 



Ser. 264, c. Fifteen 4 free larvae. 



Ser. 275, i. " " 4 free larvae; 4 degenerating larvae. 



Ser. 251, b. Sixteen " " i degenerating larva; i embryo. 



Ser. 252, b. Eighteen No asexual larvae or embryos. 



These data indicate that not more than twelve to fifteen 

 asexual larvae are produced by a single egg. They also show 

 the period in which these larvae are developed. The youngest 

 stage containing free larvae was twelve days old, while the oldest 

 was sixteen days. The asexual larvae have all degenerated by 

 the eighteenth day. This conclusion has been verified by an 

 extensive study of infected caterpillars from the field. No 

 asexual larvae have been found in caterpillars whose size indicated 

 that they were eighteen days or older. 



The general appearance of the fully developed asexual larva 

 is shown in Figs. 20-22. I have not worked out the details of 

 their organization, but it is clear from a study of entire mounts 

 and sections that the reproductive system is absent. Whether, 

 as in Litomastix, the respiratory system, circulatory system, and 

 malpighian tubules are absent, I have not determined. 



The asexual larvae apparently do not live more than a very few 

 days after being set free in the body cavity, probably not over 

 three days. Free larvae first appear on the twelfth day, and de- 

 generating specimens are found on the fifteenth day. The last 

 larvae escape from their envelopes on the sixteenth day, and dis- 

 appear on the eighteenth day. Without exception all asexual 



