Homology of the Mouth-Parts of the 

 Preimago in the Lepidoptera* 



EDNA MOSHER 



There has always been more or less discussion as to the presence 

 or absence of mandibles in the Lepidoptera. Some writers have 

 argued that mandibles are present only in rare instances and that 

 the structures thought to be mandibles are generally pillifers. Since 

 Poulton's studies on the pupal wings of Lepidoptera have shown 

 that a more generalized outline is always present than in the case 

 of the imago, and Spuler has called attention to the fact that the 

 veining in pupal wings is much more generalized than in the imago, 

 it seemed highly probable, therefore, that a study of the preimago 

 might throw some light on the question of the presence of mandibles 

 and the homology of the mouth-parts in this order. Representa- 

 tives of nine genera were studied for this purpose and the results 

 of the investigation are given herewith. 



Sthenopis thule 



A study was first made of the mouth-parts of three forms 

 selected from widely differing families. The first, Sthenopis thule, 

 an hepialid, belongs to a very generalized family of Lepidop- 

 tera, where it would be expected that all of the parts repre- 

 sented in any family of the order would be present. Although the 

 adult mouth-parts are functionless, the parts are all present in the 

 preimago and the clypeus, labrum, mandibles, maxillary lobes which 

 are doubtless the homologues of the maxillae of other members of 

 the order, maxillary palpi and labial palpi are easily identified. In 

 a cephalic view of Sthenopis thule (Fig. 1) the clypeus (Fig. 1, 

 cl) is shown occupying the central portion of the head, strongly 

 concave on the margin adjoining the labrum, with the caudo-lateral 

 angles produced, and rounded, the invaginations for the anterior 

 arms (Fig. 1, at) of the tentorium being located between these 



*Contribution from the Entomological Laboratories of the Universit\' of Illinois, 

 No. 39. 



