CUTICULA COLORS. I33 



species," and are developed in a short time one or two hours after hatching. 

 Almost as soon as the embryo emerges from the egg the primary cuticula 

 begins to harden rapidly ; and about the same time, and especially after the 

 larva begins to feed, the secondary cuticula begins to be deposited, and its 

 deposition continues until near the end of the first larval instar. The deposi- 

 tion of this second layer, however, does not completely separate the primary 

 cuticula from the hypodermal cells, a connection being retained by means of 

 the numerous protoplasmic processes occupying the pore canals of the second- 

 ary cuticula. Near the end of the larval instar the protoplasmic processes are 

 withdrawn from the pore canals, the hypodermal cells lose their attachment 

 to the lower side of the secondary cuticula, and the hypodermis and cuticula 

 separate. The ordinary process of ecdysis now removes the old cuticula ; but 

 before this is accomplished a new, fresh, colorless layer of primary cuticula 

 has developed beneath the old. 



With each succeeding ecdysis all the cuticula colors of the entire body are 

 lost and are redeveloped in the few hours immediately following. Although 

 they usually reappear in the same areas where they existed in the previous 

 stage, this process allows of variation in the coloration from instar to instar. 

 The development of the cuticula color is always the same, no matter whether 

 in a freshly hatched larva or in the transforming imago. Likewise the 

 stages are the same a cloudy appearance in the primary cuticula, and then a 

 faint yellow followed by darker yellow, brown, and black. Cessation of devel- 

 opment through any cause at any point in this series gives for the perma- 

 nent coloration that color of the stage when development ceased. At each 

 renewal of the colors the full development is attained in a short period of time 

 immediately following the casting of the old cuticula covering. 



Without exception in this genus, and, as I have shown, in insects in general, 

 the successive development of cuticula color in the ontogeny of insects fol- 

 lows the same lines laid down in the general account of the process and its 

 repetition. We shall now consider in detail the development of cuticula 

 colors in this genus. 



THE CUTICULA, ITS STRUCTURE AND COMPOSITION. 



It has been shown by Vossler and Tower that the cuticula portion of the 

 body wall of insects is composed of two distinct kinds of substances an 

 outer, homogeneous, primary cuticula, and an inner, stratified, secondary cutic- 

 ula. The inner layer differs from the outer in that it gives a cellulose reaction 

 and is akin to carbohydrates. The outer layer of the cuticula is, I believe, a 

 derivative of some gelatinate and the secondary cuticula a carbohydrate. 



Pupae of decemlincata, two to five days old, taken before pigmentation or 

 deposition of the secondary cuticula had begun, were crushed in a mortar, 

 washed in distilled water, to remove all loose material, and then macerated 

 with 1 per cent KOH for twenty-four hours at 18 to 22 C, with frequent 



