242 WOODY PLANTS OF MASSACHUSETTS. 



Insects 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 Centra 

 borealls, 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 Antiopa butterfly 

 are found in great numbers on the poplars, the willows and the 

 elm, and commit great ravages on their leaves, (ib. p. 219 — and 

 305.) So do the spinning caterpillars of the Closiera Ameri- 

 cana, (ib. p. 313), and the caterpillars of the herald-moth. 

 Still more serious injury is done by the boring grubs of the 

 beetle called Saperda calcarata, and those of the Prionus lati- 

 collis. The former live in the trunks, the latter in the trunks 

 and roots of the various kinds of poplar, native and foreign. 

 (Ib. pp. 80 and 88.) 



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. Two other species have been exten- 

 sively introduced, the Lombardy Poplar, and the White Poplar. 



Sp. 1. The Large Poplar. Populus grandidentala. 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-like appearance of the trunk. It is re- 

 markably smooth, but in very old trunks cracks a little. 



The leaves, which are often in tufts at the ends of the branch- 

 lets, are roundish, with from five to nine, large, blunt teeth 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 in 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 diameter of 

 from sixteen to twenty-four inches, and forms a small, roundish 



