Dec. 1899] Dyar: Life- Histories of N. Y. Slug Caterpillars. 239 



the head is extended. On the thorax three warts ; on the abdomen 

 two on each segment with a third rudimentarj' subventral row reduced 

 to two setos (iv and v); subprimary tubercles, as well as vii and viii 

 lost. Warts not produced, bearing hairs only after stage I, not degen- 

 erate ; no stinging spines or at least these not predominant. A primi- 

 tive first stage present, the tubercles i and ii united at base to form a 

 Y-shaped structure. Spiracles in line, normal. Warts all present. 

 Depressed spaces not present, but represented by their glandular 

 centers at least as far as those numbered (i), (2), (4), (5) and (6) ; 

 (i) paired and double on all the segments. No secondary hairs. 

 Skin minutely spinulose or possibly finely granular. There is some 

 evidence that the color was green, as both our present lowest species 

 on the two sides of the tree are green. But since the above 

 characterization fits so exactly (except for the feet) some of our 

 sparsely haired Megalopygidae and the whole Zygseno-Pyromorphid 

 group in general, I should rather expect the coloration to have been 

 like theirs, yellow with black, red or white marks. 



Concerning the origin of this generalized Eucleid, it is clearly from 

 the Megalopygid^e or their ancestors. The Megalopygidse retain 

 the abdominal feet, but they also have pads on joints 6 to 11, and it 

 is these pads, extended to joint 5 and possibly 12, which I think are 

 the homologues of the Eucleid suckers. In other respects, excluding 

 the necessary reduction of the subventral hair structures in the Eucleid, 

 there is absolutely no difference between my generalized Eucleid and 

 the Megalopygid type. 



Construction of the Genealogical Tree. 



The larvae divide at once into two groups, the " smooth " and the 

 " spined," separated not only by the differences between the tendency 

 to atrophy of the warts on the one side and hypertrophy on the other, 

 but by the peculiar structure of joint 5 in the spined group. This 

 represents a dichotomous division in the line of descent, and our 

 genealogical tree will start forked (Plate VI, Fig. 6, B and a). The 

 spined Eucleids separate into sections i and 2 of the revised table 

 given above, all those on the branch F being furnished with true 

 stinging spines and no longer feeding in stage I, which retains the 

 ancestral setae in reduced number. Branch G comprises this stock, 

 but J includes those which possess detachable spinules and correspond 

 to "type 3 " of the table. Branch C is clearly the oldest, becaase 



