1864.] 42 



there is a row of whitish, black-tipped, short spines on the inferior margin of 

 the sulidorsal stripe, placed two-thirds of the way to the tip of each segment. 

 Segment 2 has the two subdorsal spines replaced by two black, blnnt, spinous 

 horns, placed below the subdorsal stripe and one-eighth of an inch long. The 

 four superior spines of segment 11 more prominent than the corresponding ones 

 of the other segments. Segment 12 with a slightly bifurcate spine on the dor- 

 sal line, the size of the lateral ones of the eleventh segment; another in range 

 with the stigmata, the size of the substigmatal ones and having a small branch 

 posteriorly; a small intermediate one ranging with the lateral line; another of 

 the same size ranging with the substigmatal line ; and a ventral one similar to 

 and ranging with the ventral spines of segments 10 and 11; making 9 spines 

 on this segment, nearly ranging transversely. Caudal plate triangular, mar- 

 gined externally with eight black spines, the six anterior ones short, the two 

 terminal ones green at base, larger and pointing backward. Stigmata black. 

 Legs tipped with black, the anterior pair with a transversely subelliptic black 

 spot on their posterior base, the second pair with a dot similarly placed. — Feeds 

 on sugar-maple. 



From the facts referred to above and those recorded by me elsewhere, 

 we may construct the following almost unbroken series, from the first 

 dawnings of the Phytophagic A^ariety to the full development of the 

 Phytophagic Species. 



1st. Diiference of food, even when the food-plant belongs to widely 

 distinct botanical families, is accompanied by no differences whatever, 

 either in the larva, pupa or imago state. — Atfdcus Ctcropia Lin., Drijo- 

 vampa imperialls Drury, Lurhiius Cari/sc Harris, {Proc. Ent Soc. 

 Phil. I. p. 303,) and hundreds of other species. 



2nd. Difference of food is accompanied by a marked difference in 

 the color of the silk-producing secretions. — Bomhyx mori Lin., the 

 common silkworm. 



3rd. Difference of food is accompanied by a tendency towards the 

 obliteration of the normal dark markings in the imago. — Haltica alter- 

 nata lllig. 



4th. Difference of food is accompanied by marked, but not perfectly 

 constant, colorational differences in the larva, but none whatever in 

 the % 9 imago. — Datcuia ininistra Drury. 



5th. Difference of food is accompanied by a marked and perfectly 

 constant difference in the size of the imago. — Chrysomela scalaris Lee. 



6th. Difference of food is accompanied by a marked difference in the 

 chemical properties of the gall-producing secretions, the external cha- 



