592 Wm. S. Marshall, 



curved chitinoiis piece which extends for some distance down be- 

 tween the layers of hypodermis forming the wing rudiment. In Platy- 

 fhylax the secretion which was near the rudiment and extended down 

 into it was never colored. 



There has been some discussion regarding the covering by a cuti- 

 cular layer of the older wing rudiment and the young developing wing. 

 There is no doubt but that such a layer exists in Platyphylax as it is 

 easily seen on the outer surface of the hypodermal cells. When eva- 

 gination of the disk is completed and the wing rudiment is well de- 

 fined the cuticula is present and at this stage often shows a connection 

 by Strands with the inner surface of the cuticular layer which sur- 

 rounds the body of the larva. Later, after the two layers of the de- 

 veloping wing have more or less fused, sections will show a cuticular 

 covering over the entire surface of the wing (Fig. 21). In the older 

 wing the same thing is true. 



The Position at which the wing is attached to the body, relative 

 to the tergum and pleurum, is, unless there are differences in the in- 

 sects studied, something of a controverted question. Packard (10) 

 says: "The wings in all hemimetabolous insects are outgrowths from 

 the notum, and not from the flanks or pleurum of the thorax." This 

 he says also holds true of other insects. Fritz Müller (9) would have 

 the wings arise from the lateral continuations of the dorsal plates of 

 the body segments with which they are connected. Comstock and 

 Needham (2) say: "It is well kno\\Ti that the wings of insects arise 

 as sac-like folds of the body wall of the second and third thoracic Seg- 

 ments. These folds first appear at the point where the suture between 

 the tergum and the pleurum later develops. In most insects with in- 

 complete metamorphosis they are so directly continuous with the 

 tergum and become solidly chitinized with it that they have generally 

 been interpreted as outgrowths from its caudo-lateral margin." Tower 

 (16) : "In the Coleoptera the wing fundiament always occupies a position 

 just below the line where, later, the suture between the pleurum and 

 tergum will originate." From the above it will be seen that opinions 

 differ as to just where the rudiment lies in relation to the external 

 plates of the thoracic segments bearing them. 



In the larvae of Platyphylax the first two thoracic segments are 

 covered with thicker and darker cuticula than is the metathorax, this 

 is due to the last segment of the thorax being more covered by the 

 la*val Gase. Of the two wino-bearino- segments the mesothorax shows 

 the dorsal plate much more distinctly than does the metathorax and 



