188 



EXPERIMENTAL FARMS 



Fig. 11. — Aphelinus mytilaspidis. 



Fig. 10. 



3-4 EDWARD VII., A. 1904 



Oyster-siiell Bark-louse (Mytilaspis uhni, 1^=11. pomorum, Bouche) has been 



complained of from almost every part of the Dominion where fruit trees are 



grown; and the chief reason that it remains unchecked and continues to 



increase, seems to be that it is so often overlooked by fruit growers and 



others who ought to know such a common and destructive enemy by sight 



and also be well acquainted with the 



best means of fighting against it. In 



south-western Ontario excellent work 



has been done in preventing the spread 



of this scale by the minute chalcid 



parasite, Aphelinus mytilaspidis, Le- 



Baron. The presence of the parasite 



in a district can be detected by the 



minute round holes left by the tiny 



parasites where they have eaten their 



way out through the tops of the old 



scales. This minute friend is so small that it can hardly be seen with the 



rp^^,j„ unaided eye. It is bright yellow in colour, with golden eyes, and mea- 



infested with sures only about one thirty-sixth of an inch in length. Under a mag- 



p^'^i^i" ' ^^'^^^ nifyi^g glass, it is found to be a four-winged fly shaped as shown in the 



enlarged figure herewith. This parasite is sometimes so abundint that 



it destroys more than half of the scales which are formed. It has occurred in all 



parts of Canada but never seems to remain long in any district, a fact which is rather 



remarkable, as the 

 Oyster- shell Bark- 

 louse upon which it 

 feeds is 

 everywhere. 

 last year or 

 been noticed in large 

 numbers upcn fcale-i .- 

 fested fruit trees in 

 the Niagara district. 

 TJaere is only one 

 brood of the Oyster- 

 shell Bark-louse in the 

 year. The young bark- 

 lice emerge from beneath the old scale in Ontario and British Columbia about the 

 end of May, and in the maritime provinces towards the end of June. At that time 

 they are small six-legged insects resembling mites. After emerging, they wander 

 about the trees for a few hours, looking for a suitable place to attach themselves to the 

 bark, which they do by means of their slender beaks. Once having attached them- 

 selves, they never move from that place ; gradually their legs disappear, with the in- 

 crease in size of their bodies, and a waxy scale is secreted over them. By the middle 

 of August the female bark-louse has practically changed into a bag of eggs protected 

 by a scale. Little by little the body of the mother insect dries up ; and, when all of 

 her eggs are laid, the scale is well filled with these minute white objects, and the 

 mother's body is merely an empty skin at the small end of the scale. The scales of 

 the male bark -lice are seldom noticed. They are of different shape and, as a rule, 

 occur on the leaves. They are much smaller than those of the female and are long, 

 narrow and white. (Fig. 12c.) The perfect male is a tiny winged insect which is able 

 to fly well. 



Trees upon which this insect occurs, are weakened by being robbed of their 

 sap by these small insects, which frequently occur in such enormous number^ ay 



abundant 



For the 



two it has 



Fig. 12. 



-The Oyster-shell Bark-louse: a, 6, male adult ; c, male 

 scale — much enlarged. 



