5i8 ENTOMOLOGICAL NEWS. [September, 



SPECIAL STRUCTURAL CHARACTERS. 



Somewhat flattened, rounded at the ends, the sides parallel ; 

 dorsal and lateral spaces broad, subventral space narrow. 

 Ridges very slight, the subdorsal indicated b}' the change in 

 direction of slope of the body, lateral and subventral ridges 

 more distinct, approximate. Warts converted into fleshy, 

 horn-like processes, unequall}- elongated, at first long and 

 distinct, later reduced, non-functional, almost rudimentary. 

 In stage I, the horns bear each three slender setse ; after the 

 first molt, numerous urticating spines. The horns at the ex- 

 tremities are long, the central ones short ; subventral row 

 represented by two setse. Arrangement of horns exactly as 

 in Sibine stimulea (Journ. N. Y. Ent. Soc. , iv, 2). Depres.sed 

 spaces feebly developed, only their glandular centers distin- 

 guishable in the rather well-marked intersegmental incisures ; 

 but the largest ones conspicuous as they are marked with black 

 pigment. Dorsal row (i) paired, distinct; (2) slight; (4) 

 distinct ; (6) slight. Skin at first smooth, next reticularly 

 shagreened, then granular, finally spinulose. The change in 

 color to that of the mature larva occurs before the last molt 

 and the horns begin to be shortened at this time (stage VI.), 

 indicating that the pattern of marking is comparatively old 

 and fixed. The detachable spines and caltropes are present as 

 in 5". stimulea. 



The larva does not show any ancestral characters during 

 ontogeny. The horns are long at first, showing derivation 

 from a long-horned ancestor. In the earlier stages some heavy 

 black .spots appear, which, in the mature larva, are represented 

 only by the dark depressed spaces ; this is the only ancestral 

 character in the larvae that indicates a former different color 

 development, now early suppre.ssed. I do not know its sig- 

 nificance. The changes in skin sculpturing rather neatly .show 

 the probable evolution of this character in the phylum of the 

 " tropic spined Eucleidxy Thus the reticular lining is j^rimi 

 tive, now retained in Sisyrosea and the early stages of Naiada . 

 next come the granules, shown in the late .stages of Natada 

 and in linclca and Adomta ; finally the spinules of Parasa and 

 Sibine (.separately derived in these two genera). 



