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 not 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 setae. 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 few 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 12 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 setae it is very primitive. 
It belongs distinctly to the section of spined larvae from the absence of 
