Dec. 1896] Dyar : LiFE-HisTORiEs OF N. Y. Slug Caterpillars. 179 



Special Structural Characters. 



Outline rounded quadrangular, exclusive of the appendages, dorsal 

 space broad, even, flat; lateral space broad, subventral comparatively 

 broad, continuous with the lateral space, not retracted. Ridges prac- 

 tically absent, the subdorsal indicated by the change in direction of 

 slope between back and sides. Tubercles greatly modified : stage I 

 represents a primitive first stage, but tubercles i and ii on abdomen, ia 

 and ib, iia and iib on thorax are completely united into a single spine, 

 probably by a process, such as is indicated by the Y-shaped and pronged 

 setae of T. pallida and T. fasciola. Tubercle iii of joint 5 is absent. 

 After stage I the setae reappear double, normal. The ultimate structure of 

 the warts, which appear at first molt, is remarkable. The subdorsal 

 series are attached by very broad bases, greatly encroaching on the dor- 

 sal and lateral spaces, and are produced laterally into fleshy appendages 

 of different lengths. These appendages are constricted at about the 

 center of the attachment ; the basal part bears seta i in its center; the 

 terminal part bears seta ii at the apex. The lateral row of warts form 

 small, rounded, button-like structures, concealed for a long time beneath 

 the large subdorsal appendages. These warts of both rows are composed 

 of soft spongy tissue and they readily become detached at their bases, 

 leaving a small denuded area, which does nut bleed. If the appendages 

 are detached toward maturity, they are not regenerated ; but if early in 

 life a partial regeneration occurs at each molt, so that the structure 

 may attain nearly its normal appearance. The subdorsal warts are each 

 pushed a little forward so as to partially cover the segment in front. 

 The warts bear at first stiff, smooth, pale setse. Gradually a series of 

 fine, secondary, branched hairs (Plate VIII, fig. 11) appears, and in the 

 last stage, completely replaces the primary coating, leaving only the 

 primitive setae and a {&\\ club-shaped black hairs, which represent the 

 last degenerate form of the original coating. In the case of the lateral 

 horns the change from simple to fine branched hairs at the last molt is 

 more sudden. The skin is covered with a sparse coating of fine black 

 hairs from large tubercles (Plate VIII, fig. 15). The depressed spaces 

 are hardly represented at all ; the spiracular series (7) only is faintly 

 shown. The appendages are formed by the subdorsal horns of joints 4 

 to 1 2 inclusive ; all the others form warts of the small button-like type. 



This curious larva seems to mimic a dead dry leaf. In respect to 

 its adaptive characters it is highly specialized, perhaps the most highly 

 specialized of any Eucleid ; yet in respect to its set^e it is very primitive. 

 It belongs distinctly to the section of spined larvae from the absence of 



