3171 NOCTUID LARVAE— RIPLEY 75 



width during larval life. The same may be said of the loss of the portion 

 of the proximal sclerite which lies between the sensoria in the first instar of 

 Lycophotia margaritosa. Since morphological evidence indicates that both 

 the palpiger and the proximal sclerite of the spinneret in noctuid larvae 

 represent the remnants of a more general chitinization, it seems probable 

 that both of these changes are recapitulative. 



The taxonomic importance of the structure of the spinneret of the last 

 instar has alreadj^ been emphasized. It is obvious that the condition of 

 this structure in the first instar also provides valuable phylogenetic infor- 

 mation. In Lycophotia margaritosa and Agrotis ypsilon, where the spinneret 

 of the last instar is essentially of the same type, that of the newly hatched 

 larva is strikingly different. These two species are both of the subfamily 

 Agrotinae. The habit of spinning threads in the first stadium, nevertheless, 

 is apparently a comparatively fundamental one, hence the extent of the 

 development of the spinneret in this stage, which is correlated with this 

 habit promises to serve as a fundamental guide to relationships. It is 

 important, therefore, that all accounts of the development of caterpillars 

 state the situation with regard to the form of this organ and with reference 

 to the spinning of threads m all itistars. On the basis of the limited amount 

 of data available as to the occurrence of silk-spinning in the first instar of 

 noctuid larvae no correlation with the mode of life is apparent. 



LARV.APODS 



In the morphological discussion of the larvapods it was noted that the 

 ancestral condition, where the four median pairs are well-developed, has 

 been retained in the majority of noctuid larvae, altho in certain sub- 

 families the first one or two pairs tend to become reduced and are sometimes 

 lacking. The incipient condition in the development of this specialization 

 is exemplified by many Agrotinae, where the first two pairs are distinctly, 

 altho not strikingly shorter than the others. In Catocala a more advanced 

 condition is found, the first two pairs of larvapods being much smaller 

 than the others. This process has proceeded still further in the specialized 

 subfamily Hypeninae, where the first pair is without crochets or wanting 

 altogether. The most specialized situation with respect to this process is 

 exhibited by nearly all Phytometrinae, whose adults are undoubtedly 

 among the most specialized noctuids, and by certain Catocalinae, such as 

 Caenurgia, where the larvapods of only the fifth and sixth adbominal and 

 of the anal segments remain. 



If the postembryonic development of the larvapods were to recapitulate 

 their phylogeny, we should expect to find a relative decrease in the size of 

 the first one or two pairs from the first to the last instars in forms where 

 these larvapods are reduced in size in the fully grown larva. In species 

 where the last instar lacks the first one or two pairs they would be found, 



