407] COLORS OF TIGER BEETLES— SHELFORD 



ANALYSIS OF COLOR PATTERNS 



COLOR PATTERNS AND ELYTRAL STRUCTURES 



In the Cicindelidae usually onlj' the elytra have color patterus. 

 These are merely sack like outgrowths supplied vAih. nerves, trachea, 

 and blood spaces. The cutieular covering is in two layers;, the outer 

 portion is a hard and relatively homogeneous layer known as the primary 

 cuticitla and on the upper side is usually characterized by the presence 

 of saucer-shaped depressions, somewhat hexagonal in form, fitting to- 

 gether with common rims. These rims usually correspond to the posi- 

 tions of the points of contact of the hypodermal cells and accordingly 

 each cup corresponds to a cell (Packard, 1900 text). Some forms in 

 the family, e. g., the Tetraehas and the Amblychilas do not have these 

 cups; the surface is smooth. In certain areas the primary cuticula is 

 pigmented and in certain areas clear and transparent. This gives the 

 color pattern. Some species are almost entirely pigmented ; some entirely 

 without pigment. Beneath the primary cuticle is the secondary cuticula 

 which is laid down in successive layers during the life of the individual 

 and in the forms like Ambli)chila cylindriformis, and Phaeoxantha 

 klugi is essentially uniform in character. It contains some spaces, prob- 

 ably pore canals, which are empty of cell contents except for the layer 

 in actual contact with the cells. A few of these pore canals can be 

 detected in the secondary- cuticula of Tctracha Carolina. In Cieindela 

 the secondary cuticula beneath the pigmented areas of the elytron is 

 clear and transparent and entirely free from the "pore canals" and 

 interlamellar spaces, while beneath the unpigmented areas it is full of 

 the "pore canals" and large interlamellar spaces, and these having 

 been left empty by the retreat of the cells from the successive layers; 

 they give the effect of a white or straw color depending upon the color 

 of the secondary cuticula itself. In these regions, beneath the unpig- 

 mented primarv cuticula, it is about twice as thick as beneath the 

 pigmented parts (Fig. 1, PI. I). The color pattern may accordingly 

 be described in terms of pigment and lack of pigment, the so-called 

 markings being without pigment. 



The two walls of the sac-like elytron are held together by chitinous 

 pillars or columns which in the adult appear in cleared elytra. The 

 different lavers of cuticula show here as rings around the original 



