31 
and trees in winter. It may also be practicable to protect trees espe- 
cially exposed by painting rough, knotty, and injured places on the 
bark with a poison mixture commonly used by orchardists to prevent 
infestation by ordinary borers. A number of substances are avail- 
able for this purpose, the simplest of which, perhaps, is a mixture 
of soft soap and soda, with the addition of Paris green. The fol- 
lowing is a convenient formula : To a saturated solution of wash- 
ing soda add soft soap sufficient to make a thick paint, and to each 
ten gallons of this wash add a pint of crude carbolic acid and half a 
pound of Paris green. This may be painted thickly upon scarred, 
roughened, or knotty surfaces in April and early May and renewed 
as necessary until August. 
Two Poplar Borers 
(Mciiiythrus triciiictus Harris) 
(M. dollii Neum.) 
Two boring caterpillars, similar in appearance, but differing in 
the larval or boring stage mainly in size, infest poplars in this state 
to an injurious degree. They are most destructive to young nursery 
trees, particularly to the balm of Gilead (Populus candicans) , but 
the Carolina poplar {P. deltoidcs), Figure 30, is also sometimes 
badly infested. They are generally present thruout Chicago, often 
infesting trees which are likewise injured by a boring larva, Cryp- 
iorhynchus lapatJii. discussed on p. 40. They have also been found 
by us in park and street trees in several Illinois cities and towns 
from Centralia northward. In the case observed by us in Chicago, 
the eggs of one of these species, which one we do not know, were 
deposited July 22, mostly in a crevice of the bark or in the neigh- 
borhood of a bud, and young larvje were first seen July 26, altho 
some of these had apparently hatched at least a week before. The 
borers winter in the larval stage in the wood, pupate in spring, and 
come out as winged moths in June and July — at various dates from 
June 18 to July 26, if we may judge by results obtained in our in- 
sectary. From a willow in Cook county a specimen of M. tricinctiis 
was bred which emerged July 2. 
The boring larvse are whitish caterpillars, with brown or yellow- 
ish heads and a smooth neck shield. The two species are most easily 
distinguished by the markings of the head and by the number of 
hooks on the abdominal legs. In 71/. tricinctits the head is yellowish 
and mottled with large patches of brown, while the abdominal feet 
have from eighteen to twenty-two hooks in a row. In M. dollii 
