242 WOODY PLANTS OF MASSACHUSETTS. 
Insecis on the Poplars.—The large, pea-green, stinging cater- 
pillars of the moth called Saturnia Io, feed on the leaves of the 
balsam poplars, as well as on those of the elm, the cornel and 
the sassafras. (Harris, p. 283.) ‘The caterpillar of the Cerura 
borealis, remarkable for his odd appearance and horned tail, and 
thence called the horn-tailed caterpillar, also feeds on the sev- 
eral species of poplar. ‘The caterpillars of the Andiopa butterfly 
are found in great numbers on the poplars, the willows and the 
elm, and commit greatravageson their leaves, (1b. p. 219—and 
305.) So do the spinning caterpillars of the Clostera Ameri- 
cana, (ab. p. 313), and the caterpillars of the herald-moth. 
Still more serious injury is done by the boring grubs of the 
beetle called Saperda calcaraia, and those of the Prionus lati- 
collis. 'The former live in the trunks, the latter m the trunks 
and roots of the various kinds of poplar, native and foreign. 
(Ib. pp. 80 and 68.) 
Four species of poplar are native to Massachusetts, the Large 
Poplar, the American Aspen, the Balm of Gilead, and the River 
or Smooth-leaved Poplar. ‘'T'wo other species have been exten- 
sively introduced, the Lombardy Poplar, and the White Poplar. 
Sp. 1. Tsar Larce Portar. Pdpulus grandideniata. Michaux. 
The leaf and fertile ament figured in Michaux, Sylva, II, Plate 99, fig. 2. 
This is a tall, erect tree, covered with a smooth bark of a 
soft, light, greenish gray color. ‘The branches are small, and, 
although they go out at a large angle, rarely form a broad 
head. ‘The bark on the young branches is dark, but soon takes 
the uniform, leather-lke appearance of the tiunk. It 1s re- 
markably smooth, but im very old trunks cracks a hittle. 
The leaves, which are often in tufts at the ends of the branch- 
lets, are roundish, with from five to nine, large, blunt tecth on 
each side, smooth on both surfaces, and paler beneath. ‘The foot- 
stalk is slender, compressed laterally, two thirds as long as the 
leaf. The buds are conical. 
This tree is found abundantly growing 1n the forests in the 
western and northern parts of the State, in which situation it 
rises to the height of seventy or eighty feet, with a diametei of 
flom sixteen to twenty-four inches, and forms a small, roundish 
