22 ILLINOIS BIOLOGICAL MONOGRAPHS [264 



ological evidence indicates that the semicircular sclerite was originally a 

 complete ring, its reduction having begun on the meson and proceeded 

 laterad. Its shape varies much within the family affording generic and 

 specific characters. The proximal fold, which assumes a great variety of 

 forms within the order, also exhibits marked differences within the family, 

 ranging from membranous and rounded, the more usual condition, to 

 chitinized, long and pointed, when it serves as a support (Fig. 32) for the 

 spinning organ, which lies caudad of its caudal surface. This is the situa- 

 tion found by Dampf in the psychid genus Eumeta, which presumably led 

 him to believe that this structure represents the paraglossae. 



In three European species of Hepialus examined the spinneret is 

 exceptionally long, tubular, and tapering, almost filiform, extending 

 several times the length of the labial palpi. According to Packard it is well 

 developed in Micropteryx, but his figures of the larval heads of Eriocephala, 

 drawn from a few poorly mounted specimens, fail to show any spinneret. 

 Most commonly throughout the order it is tubular, slightly tapering, 

 truncate, and distinctly longer that the palpi. It is often supported 

 (Fig. 32) by longitudinal chitinized areas, as in Polia renigera. In certain 

 groups, notably the Sphingidae, Noctuidae, and Nepticulidae, it is short, 

 flat, and stubby, frequently exhibiting a peculiar fringe (Figs. 26, 38, 39, 

 45, 46) in the two former families. When of this type in the Noctuidae the 

 spinneret is often emarginate on the sides so that an upper and lower lip is 

 formed, the latter usually being the longer. The lower lip may be deeply 

 emarginate, as in Cirphis unipunda (Fig. 27) or bilobed, as in many Agro- 

 tinae. Both lips or the upper one only may be fringed. All stages in the 

 development of the fringe are represented by various species of noctuid 

 larvae. It appears to have developed on the upper lip earliest in phylogeny 

 (Figs. 45, 46) appearing later (Figs. 26, 39) on both surfaces. 



With the exception of the subfiliform t3T3e of Hepialus, all forms of 

 spinning organ observed in other families are represented within the Noc- 

 tuidae, this family probably presenting a greater range of variation in its 

 spinneret than any other. In the Agrotinae it is often much shorter than 

 the palpi, flat, with upper and lower lips, and frequently bilobed or fringed, 

 or it may be long and pointed, as in Chloridea. It ranges from long and 

 slender to fairly stout and about equal to the palpi in length in the Hadeni- 

 nae, being either truncate and fringed, as in Cirphis unipunda, or pointed, 

 as in Moliana albilinea. Most commonly it is distinctly longer than the 

 palpi in this subfamily and is apparently never markedly shorter, as it is 

 in the Agrotinae. In the species of Cucullinae, Phytometrinae, and Hy- 

 peninae examined it is much longer than the palpi and usually tapering. 

 It distinctly exceeds the palpi in length in the Catocalinae, where it ranges 

 from stout to slender. The spinneret of the Acronyctinae varies from 

 slightly to greatly longer than the palpi, presenting an extensive variety of 



