ONTARIO DEPARTMENT OF AGRICULTURE. 
 
 TORONTO, ONT. MAY 1. 1898. 
 
 THE SPRUCE GALL-LOUSE. 
 
 {Chermea abietis.) 
 Prepared for the Bureau op FeRssTRY by Wm. Brodie, Toronto. 
 
 In the spring of 1897 many spruce trees in and around Toronto were found 
 to be more or less injured by a pseudo-gall insect. The galls were enlarged and 
 deformed buds of the previous year, usually towards the tips of the twigs. 
 Investigation showed that these galls were formed by a small insect popularly 
 called the spruce gall- louse, the Chermes ahietes of entomologists. A short 
 account of this destructive pest, as then known in Ontario, appeared in the 
 annual report of the Olerk of Forestry for the Province of Ontario for 1897. 
 ISince then it has spread with astonishing rapidity and has been detected at 
 many points, from Peterborough to the county of Bruce, where it was lately 
 detected by Dr. Hunter on native spruce trees in a swamp in the township of 
 CulrosB. It has also been found ou native spruces in Muskoka, near Utterson 
 station. So far it would appear that unless this insect is checked by some 
 artificial means it will soon destroy our ornamental spruce trees and hedges and, 
 extending northwards, do immense injury to our spruce forests. 
 
 The trees already attacked by this spruce gall-louse in Ontario are the 
 European spruce, Picea excelsa, the double spruce or black spriico, Picea nigra, 
 the white spruce, Picea alba, and the balsam fir, Abies balsartiea, and it may also 
 be found on the hemlock, Tsnga Canadensis. This insect is native to Northern 
 Europe and was introduced into the United States on imported spruce trees and 
 thence into Ontario, or it may have been introduced here direct from Europe, 
 as for many years there has been an annual importation of young European 
 spruce trees into Ontario. 
 
2 
 
 At Toronto the full grown insects — the producers — emerge from the galls, 
 the scales of which open to give them exit, about August Ist On emerging 
 they are slightly imperfect, but in one ' day ample wings are developed which 
 enable them to fly long distances, After distribution the female settles on a 
 spruce leaf and lays — under herself — about thirty-five eggs and then dies, 
 resting on the eggs. In about a week the young six-footed larvae are hatched. 
 They crawl about and find immature buds into which they burrow and of course 
 remain quiescent during the winter. But in the following spring their presence 
 in the bud causes it to develop into a " gall " instead of a normal twig. The lice 
 in the galls give birth to other living lice so that about thirty individuals are 
 found under each scale of the gall. The galls are usually irregularly spherical 
 and often more than a half inch in diameter. When growing they are of a 
 yellowish green color, but during the winter they assume a reddish brown tint, 
 which they retain until the end of May, when they usually fall from the tree. 
 This is the usual form of this gall but there is another form, not a gall, in which 
 the injury is done in the leaf axils. As these insects in the feeding stage are 
 within the gall, and the gall is perfectly water tight, so that no fluid can pene- 
 trate, poisoning is out of the question, and as in the migrating larval stage, they 
 do not eat, poison is equally useless. Of course in this larval stage soap emul- 
 sions might be of some use, if applied abundantly at the proper time. But 
 without any doubt the cheapest and best plan as yet tried in Ontario is to clip 
 off the galls as soon as they are noticed — say in June — and always hefore the first 
 of Anguiity while the producers are in the galls, and immediately burn them up. 
 When a tree is too much infested to be dealt with in this way it should be cut 
 down and burnt at once. Of course there is no use in doing this after the 
 producers are out of the galls. Several cases are known where this plan was 
 carried out with very satisfactory results, and it is respectfully recommended 
 that ail those having spruice trees in charge should carefully see to the clearing 
 of their trees and the extermination of this formidable insect pest. As some of 
 our nurseries are aflfected, buyers of evergreen nursery stock should be very 
 careful to see that the young trees are perfectly free from this insect pest. 
 
 Description of Plate. 
 
 Fig. 1. Gall infested twig as usually seen in the fall season before the death 
 of the part of the twig above the gall. 
 
 Fig. 2. Infested twig of European spruce, two-thirds natural size, collected 
 April 16, 1898, from a badly infested tree growing in one of the Toronto 
 public pa'ks, showing the parts of the twigs above the gall dead, the leaves 
 having fallen off, the usual condition found in the spring season. 
 
 Fig. 3. Mature, winged fertile form, from a microscope mount, enlarged 
 25 dia., collected September 1, 1897. In this final stage of development they 
 do not eat, but their ample wings enable them to fly long distances before 
 ovipositing, and hence the alarmingly rapid distribution. 
 
 Fig. 4. Immature gall producer, from a microscope mount, enlarged 25 dia., 
 imm-^diately after issuing from under the scales of the gall, August 18, 1897. 
 
Fig. 1. 
 
 Fig. 2. 
 
 Fig. 3. 
 
 Fig. 4 
 
It is also respectfully requested that whoever finds these galls on 
 their trees should communicate the fact and all particulars so far 
 as ascertained, to the 
 
 BiREAr OF FORESTRY, 
 
 Parliament Buildings* 
 
 Toronto.