l62 COLORATION IN LEPTINOTARSA. 



The normal position of the wing is that in which the axis forms a high 

 angle with the longitudinal axis of the body and is not parallel with it, as some 

 writers have claimed. Each wing is composed of three clearly marked areas : 

 First, the anterior, which is supported by the costal and subcostal veins and 

 which we shall call the anterior system; second, the middle area, devoid of 

 veins, or the discal cell lying between the subcostal and ramous veins ; and 

 third, the area supported by the ramous, cubitus, medius, and anal veins, which 

 we shall call the posterior system. Each of these areas is clearly seen in the 

 wings of all insects, and even in the specialized elytra of Coleoptera (see text- 

 fig, lo). In text-figure lo c are represented these areas in the wing of a but_ 

 terfly, and in text-figure lo b in the hind wing of a Leptinotarsa. Although 

 there are great differences between these, the homologous areas are clearly 

 seen. In text-figure lo a the elytron, although specialized, shows the anterior 

 system condensed and crowded into the costal border, the tip of which is 

 further bent caudalward until it meets the anterior vein of the posterior 

 system, the ramous. At the junction of these the apex of the elytron is 

 formed, and between them is inclosed the discal or central space. Posteriorly 

 the anal and cubital veins are crowded together. In the elytron the costal 

 border is not diminished, but the margin (text-fig. lo a) is obliterated, and 

 the costal border and the outer extremity of the posterior system meet, while 

 the anal area is condensed. The least modified area of all is the central or 

 discal area. This is often divided, almost always in many orders, by a trans- 

 verse vein from the subcostal to the ramous (text-figs. lo a and lo b), and in 

 the el3^tra of beetles this position is marked in many genera and families by a 

 cross vein of varying size and distinction. Although highly specialized, the 

 elytron is clearly homologous to the wings of other insects. 



In the ontogeny of elytral coloration I have shown that color appears ear- 

 liest at the proximal portion of the wing in the interspaces between the veins, 

 and first of all in the central space, and that from these beginnings it spreads 

 distalward in species with color stripes between the veins, and across the veins 

 in unicolorous species. Of importance is the fact that in Coleoptera, as in 

 Lepidoptera, as has been shown by numerous writers, color should first appear 

 in the interspaces between the veins at the base of the wing, in the cen- 

 tral cell, and the area immediately anterior and posterior thereto. There is 

 therefore between the wings of these orders a complete homology, not only of 

 the larger parts, but also of the initial stages of color development. In the 

 further development of the color pattern of the wings of these beetles it 

 appears from the observations given that color, whether it be spot or stripe, 

 develops first between the veins and later over them. In this they are in per- 

 fect accord with the Lepidoptera. In the development of the transverse bands 

 of spots, which represent a system not found in Lepidoptera, color is found 

 over the veins. These transverse bands of spots consist of the basal band at 

 the proximal end of the wing, the distal band at the apex of the wing, which 



