30 ILLINOIS BIOLOGICAL MONOGRAPHS [424 



sary correlation between the veins and the tracheae. The greater hard- 

 ening and more general pigmentation of the veins of many insects 

 already mentioned (page 16) leads to a spotted type of wing, in many 

 cases at least. Such a system offered in the elytra of the tiger beetles 

 gives the basis for the spotted type of elytron which we find frequently 

 in the group. Veins no longer occur definitely longitudinally and the 

 tracheae do not ordinarily bear any definite relation to cross areas. 



A large background of evidence is presented above for the selection 

 of the spotted type of tiger beetle pattern, made up of spots falling into 

 rows and forming stripes and rows 5 forming cross bands, as a general 

 one from which other types are derivable by the loss of spots, com- 

 bination of spots, etc. Comparable analyses were presented by Eimer 

 (1895) and Von Linden (1902), who note cross bands as the basis of 

 the patterns of various species of Lepidoptera. Tower (1906) reduced 

 the general plan of markings in Leptinotarsa to cross bands and longi- 

 tudinal stripes. He recognized 4 or 5 unpigmented cross bands and 6 

 longitudinal unpigmented stripes which fall in the lines with the 

 tracheae instead of between them as in in Cicindelidae. He shows the 

 stripes divided into two in the area between the costal and subcostal 

 tracheae (Tower, 1906:228, Figs. 5 to 8, PL XXIV), which is com- 

 parable to the condition suggested in the carabids and dytiscids shown 

 in figures 35, 38, 39, and 40, plate IV. Tower adhered to a theory often 

 held by embryologists, namely that the base of the wing is oldest; 

 further, that pigment appears first in the base of the elytron and pro- 

 ceeds to the distal portion in accord with the relative age. No 

 conclusive evidence is brought forward to show that the base of the 

 elytron is actually oldest, and an examination of Tower's figures (Tow- 

 er, 1906: 156, Figs. 1 and 2, 7 and 8, PL 19) shows that the basal part 

 of the elytron in some species is not first pigmented. Pigment begins 

 in the costal border of the wing and at the level of the second dark 

 cross band which he calls the "proximal" and which is very common 

 in his group. This is comparable to the early stages in Cicindela (Fig. 

 111). The view that pigment comes in first in cuticula over the oldest 

 tissues from the embryonic standpoint seems not to hold good in Cic- 

 indela, for on this basis certain abdominal sclerites would be embry- 

 onicly older than others (Figs. 102 to 104, PL A 7 III), the last abdominal 

 segment older than the first, and the femur younger than the tibia as 

 well as other peculiarities shown in figures 99 to 103. The law cannot 

 be said to hold good at all in the group under consideration, but rather 

 as has been noted on page 24, there is an order of post embryonic 

 development of adult organs, which coincides with pigmentation. 



One of the most recent color-pattern analyses (Braun, 1914) shows 

 the pattern of Lithocoletes (microlepidoptera) to be made up of a mod- 



