The Genus Hylastes, Er. 158 
is obvious in that it is impossible to distinguish young and old broods in 
the field. 
Year | Jan. | | Feb. Mar. “April May pa _ July | Aug. nnd ee Oct. | Nov. | Dee. 
H. ater 
1915 so ee 
Tone Oo a Ola ©) 
1916 j++4+)/+t++)+ ++) tt+)+4t)t++4/+t++/4++4+)4+44]4+4++ 
DOO OOOMOO|O@+/++4+/+4+4+)/+4+4/4+4+4+)/4+4+414+4++ 
a -|)---/. -@/©@ |+++]/+++ 
++4+i/+ +4 +++ 
bs 2 ape Fraley Rene eee Wie ial eae ards} . <ee OE 
b ae ee |e es 
| | | 
H. palliatus 
1915 +++/44+4+l44+4 
———— @ eS 
1916 Mh rv alte hte tet ae hele es 
= —-|--@/++4+/++4+]/4+4+4]/4+4+4)/4+4+4]4+4++ 
a —-|---@]/--@je@+)/++4+)/+4++ 
@ @+ |++4+)+4+4+}4+4++4+ 
| b mote OOK 
(LEDS Se Rie OS ota ie eR ee Ly Aa atta cence ta (eae s 
In the above table, it will be seen that the most interesting period in 
the life-histories is that extending from May to September—the months 
May, August, and September being of special interest. Both species produce 
two broods in the year (marked as a and 0 in the table). In the case of H. ater 
only brood a matures. It does not give rise to a third brood, and brood 0 
attains only the larval stage (it probably endures all winter). In Z. palloatus 
brood a matures and gives rise to a third brood, a1, which reaches the larval 
stage, while brood } also matures. In my laboratory experiments it reached 
the pupal stage, when untoward circumstances caused the pupz to shrivel. 
I have no doubt that they would shortly have emerged. 
ECONOMIC IMPORTANCE OF THE GENUS HYLASTES.’ 
From the point of view of the forester, the three species of Hylastes 
under consideration may be divided into two groups—H. ater and 
H, cumicularwus forming the first, H. palliatus constituting the second. 
HA. ater and H. cunicularius. 
These two species are essentially enemies of the young newly-formed 
coniferous plantations, and more especially of such as are formed on 
