36 ILLINOIS BIOLOGICAL MONOGRAPHS [278 



There appears to be no very definite correlation within the family between 

 the mode of life and the loss or reduction of the first two pairs of larvapods, 

 although this condition is accompanied by the habit of walking with a 

 looping gait and of moving more rapidly, a point to be discussed in connec- 

 tion with the postembryology of the larvapods. The lengthening, however, 

 of the two latter pairs of median and of the anal ones, which is so pro- 

 nounced in larvae of Catocala, appears to be a modification for arboreal 

 life. The same specialization is found to a lesser degree in many arboreal 

 caterpillars. This tj^pe of larvapod seems to be found only in larvae that 

 climb extensively. The fact that the development of this modification has 

 proceeded further in the catocalas than in most other arboreal larvae is 

 consistent with the occurrence in this genus of a number of marked adapta- 

 tions to hfe in the tree stratum of the deciduous forest. The eggs, larvae, 

 and adults are protectively colored like the bark of the trees on which they 

 rest. Practically all of the species feed upon the foliage of deciduous trees 

 or upon plants of the deciduous forest. 



The number of crochets is larger in Catocala than in most noctuid 

 larvae, which is apparently a further specialization for climbing on the 

 trunks and twigs of trees. From the first to the anal pair of larvapods 

 respectively the number of crochets in Catocala grynea is 30, 36, 43, 55. 

 The other extreme is presented by some of the subterranean forms, Feliia 

 gladiaria having 8, 12, 14, 14, 18 and Sidemia devastatrix 12, 14, 14, 14, 14. 

 In general the anal pair has the largest number and the first pair often 

 bears a few less than the others. The formula for Cirphis pliragmitidicola, 

 22, 24, 26, 30, represents an average one for the family. Some individual 

 variation occurs in this respect, the number varying two or three each way 

 from the mean. It is frequently different on the two sides of the same 

 individual, as Dampf has shown it to be in the psychid, Eumeta. Con- 

 siderable difference in the number of crochets is sometimes e.xhibited by 

 closely related species, Polia meditata having 16, 18, 18, 20, 26, and renigera 

 12, 12, 16, 18, 19. These two species are decidedly subterranean. The 

 closely related Ceramica picta, on the other hand, which enters the soil only 

 to pupate, frequently climbing shrubbery to feed, has 26, 27, 30, 32, 35. 

 Beyond the presence of a larger number in the arboreal forms, there appears 

 to be no marked correlation between the mode of life and the number of 

 crochets, altho the smallest number is apparently best represented among 

 species which burrow in the soil. Specific determinations may often be 

 facilitated by these formulae, altho a considerable difference in this respect 

 according to the instar necessitates a positive knowledge of the stadium 

 before applying this character. 



