267] KOCTUID LARVAE— RIPLEY 25 



secretion of the silk-glands over the inner surface of the earthen cell. 

 Examination of the inside of these cells seems to reveal the presence of such 

 a substance. This lining serves perhaps to render the cell waterproof or to 

 prevent it from crumbling. The burrows leading to the pupal cell of 

 Cliloridea armigera have been observed to be fortified with a similar 

 secretion of unknown origin, although the spinneret of this species bears no 

 fringe. Chapman observed that the thread spun by the flat short spinneret 

 of the earlier instars of the leaf-miner, Liniacodes tcsludo, assumed the form, 

 not of a thread but of "a very thin ribbon," indicating that the semifluid 

 silk may issue from the spinneret in different physical states. A micro- 

 scopic study of the silk of noctuid larvae, as well as an investigation of the 

 comparative morphology of the silk-press promises to throw light upon 

 this question. 



Both morphological and biological evidence indicates that the long 

 cylindrical spinneret represents the ancestral condition for the Noctuidae. 

 The development of this tv-pe to a very marked degree in Hepialus, the well 

 developed spinneret inMicropteryx,and the general occurrence of the long 

 spinning-organ throughout all caterpillars seem to justify this conclusion. 

 As previously stated, the widespread distribution of the silk-spinning habit 

 throughout trichopterous, hymenopterous, and lepidopterous larvae and its 

 appearance in those of certain dipterous families indicates its development 

 at an early phylogenetic period. Its absence or reduction in members of 

 these orders may reasonably be regarded as a specialization. Since the loss 

 or reduction of this habit in noctuid larvae, which is evidently a biological 

 departure from the ancestral condition, is generally correlated with the 

 short, flat spinneret, we must conclude that this type of spinning-organ is a 

 specialized one derived from the tubular tj-pe in correlation with sub- 

 terranean pupation. 



PREPHARYNX 



The hypopharynx of caterpillars has been largely neglected, the sole 

 morphological studies of this structure having been performed by Tragardh 

 on the leaf-miners, where it frequently presents a highly modified condi- 

 tion, and by DeGryse, who has written a brief paper on this subject, 

 embracing a number of famihes. The only detailed figures of the normal 

 hypopharynx of lepidopterous larvae known to the author are those by 

 Dampf of two species of case-bearing caterpillars, and a few by DeGryse. 

 It assumes the form of a large membranous lobe lying cephalad of the 

 labium and continuous with it, and extends dorsad as a rather low mound 

 forming the lower floor of the prepharynx. A narrow sclerite continuous 

 with the chitinized portion of the stipula extends longitudinally on each 

 side of its proximal end, corresponding apparently to the lingula shown by 

 Yuasa. In many noctuid larvae the hj'popharynx is distinctly divided into 



