323] yOCTUID LARVAE—RIP LEV 81 



ization in the proximal sclerite of the spinneret; the migration mesad of the 

 proximal seta of the labial palpus in Lycophotia; the secondary appearance 

 of the tubercle of the seta rho in certain phytometrids. 



(II) Non-recapitulative.^ — (a) Adaptive to unequal function in dififerent 

 stadia.— Changes in the form of the setae of the head and trunk and in the 

 relative length of the spinneret; the acquisition of the first pair of larvapods; 

 the increase in the relative size of the first two pairs of larvapods; changes 

 in the position of the setae of these larvapods. (b) Due to the mechanics of 

 growth.— The decrease in the relative size of the head, ocellarae, and sen- 

 soria; the migration ventrad of the head-setae v2, v4, and v5; the increase 

 in the number of the crochets of the larvapods of the fifth and sixth 

 abdominal segments. 



(III) Compound, (a) recapitulative-adaptive.— The appearance of the 

 adfrontal sutures; of the fringe, lips, and secondary chitinization of the 

 spinneret; the elongation of the proximal fold of the spinneret. Compound, 

 (b) adaptive-mechanical.— The increase in the number of crochets of the 

 first two pairs of larvapods. 



(IV) Problematical.- Changes in the form of the antennae, in the 

 relative size of the setae of the stipula, and in the form of the labial palpi; 

 the reduction of the setae of the labial palpi and antennae; the loss of the 

 tubercles of the body-setae. 



. (12) The great value of a comparative postembryological study of 

 species as a source of phylogenetic information has been demonstrated, 

 chiefly by means of a detailed investigation of the development of the 

 epicranial stem. 



(13) Different types of postembryonic development of various struc- 

 tures, especially of the spinneret, epicranial stem, and larvapods, furnish 

 developmental characters of considerable taxonomic importance. The 

 condition of these structures should be given in detail in all descriptions of 

 young caterpillars. The relative length of the spinneret of the first instar 

 is especially important. The postembryonic development of the epicranial 

 index offers an excellent means of determining relationships. 



(14) Various correlations between structural and biological postem- 

 bryonic changes have been established, such as those between the relative 

 length of the spinneret and the amount of silk spun in different stadia, 

 between the development of the fringe of the spinneret and the habit of 

 subterranean pupation, and between the acquisition or relative increase in 

 size of the first pair of larvapods and the decrease in general activity. 



(15) The correlation between the subterranean mode of life, the resist- 

 ance to submergence in water, and the short epicranial stem has been 

 demonstrated. By virtue of this relation the postembryology of the 

 epicranial stem has revealed the progressive nature and independent origin 

 of the subterranean habit of noctuid larvae. 



