6o4 Vernon L. Kellogg. 



the sex of the larva can be distinguished by the character of its 

 developing primary reproductive organs, at least immediately 

 after the first larval moulting, if not, indeed, immediately after 

 hatching. 



The character of my experiments is as follows: a number of 

 small lots of larvae were taken, variously after the second, third 

 and fourth moultings, and by means of a hot needle the right or 

 left reproductive organ (ovary or testis) or both organs, were 

 burned out. The developing reproductive organs in the larvae 

 lie just underneath the body wall of the fifth abdominal segment, 

 and their position is indicated by a pair of small grayish tubercles. 

 The slight wounds made by searing soon closed and the larvae 

 were reared to moths. Many larvae died, especially among the 

 earlier lots treated, some of these deaths being undoubtedly due 

 to the mutilation. Sometimes the needle penetrated too deeply, 

 searing the wall of the alimentary canal; sometimes the dorsal 

 vessel (heart) lying very near the reproductive glands was injured; 

 sometimes the destroying of the gland itself seemed sufficient to 

 produce death. On the other hand in a very few cases I did not 

 succeed in destroying the gland, or succeeded in searing away but 

 part of it. But the results as a whole show very definite uni- 

 formity of result and afford positive conclusions. 



Eight lots of larvae of from five to twelve each were used, two 

 lots being taken just after the second moulting, three after the 

 third, and three after the fourth. In three of the lots the right 

 reproductive gland was seared in each larva, in three the left gland 

 was seared and in two the glands on both sides were seared. A 

 few larvae when full grown were dissected to note the condition 

 of the reproductive glands. From the others eighteen moths 

 were obtained. These moths were killed and dissected; in sixteen 

 moths, including males and females, there was no trace of those 

 reproductive glands, left or right or both, which had been seared 

 in the larvae; in one male moth, both testes were perfect (un- 

 doubtedly a "miss" in the searing), in another male one testis 

 was perfect while the other (seared in the larva) was very small 

 and incomplete (either a case of regeneration or more probably 

 a case of partial development of an incompletely destroyed larval 



