104 THE REPORT OF THE No. 36 



a fine, -whitish hair or bristle arises. The legs, as in the case of T. bimaculatiLS, do 

 not differ much in length. The front pair is he'ld extended in front of the body- 

 when at rest. 



From this descrij^tion it will he noticed that the easiest way of distinguishing 

 this species from T. bimaculatus is the presence of the whitish tubercles on the 

 dors-um, each with its fine hair. These tubercles are not present in the latter species. 



Copulation was n(>t observed, but smaller, more slender, adult mites, evidently 

 males, were frequently seen caressing females after the manner of the males of T. 

 bimaculatus. These resembled very closely the males of the latter species, and were 

 yellowish-white anteriorly with darkened abdomen, sometimes strongly tinted with 

 red. 



Distribution in Ontario. 



I have found the mites very widely distributed through the Province from 

 Prince Edward County on the east to Lambton County on Lake Huron on the west, 

 and from Guelph in the north to St. Catharines in the south. There seems, there- 

 fore, very litle doubt that further observations will show that they occur all over the 

 fruit growing parts of the Province. 



Pood Plants. 



Up to the present this Red Spider has been found on European plum, apple, 

 sour cherry, pear, peach, hawthorn, mountain ash and rose. It probably occurs also 

 on sweet cherry and Japanese plum. The favorite host plant by far is the European 

 plum, and in searching one is always sure to find it on the leaves of this tree if pre- 

 sent anywhere in the orchard. The apple is apparently the next choice, and then 

 sour cherry. Pears, peaches, mountain ash and roses are very little attacked in my 

 experience, and Japanese plums alongside European varieties have apparently been 

 untouched. A few hawthorn trees have been badly attacked, but these seem to have 

 been exceptions rather than the rule. No other plants have so far been seen to be 

 infes"ted. 



Nature and Extent of the Injury. 



The injury is caused in the same way as that of the Red Spider, Tetranychus 

 bimaculatus, and resembles this to a large extent. Feeding, however, takes place 

 on both surfaces of the leaves. Badly infested plum and apple foliage looks at a 

 distance as if it had been covered with very fine road dust. On closer examination 

 it can be seen that the upper surface of the leaves is studded thickly with fine white- 

 ish blotches. With the further feeding of the mites many of the leaves turn brown- 

 ish, thus giving the foliage the dusty appearance just referred to. Whole plum, and 

 in a few cases, whole apple orchards, have been affected in this way. Often, however, 

 only a few of the trees are severely attacked, and sometimes very little damage is 

 done. Some seasons the mites are much worge than others. They were worse last 

 year at Guelph and in Niagara than this year. It is difficult to estimate how much 

 damage even a bad infestation causes. Perhaps as much as one should say is that 

 it must interfere considerably with the function of the leaves in manufacturing food, 

 and so weaken the tree and lessen its power of producing large crops of good sized 

 fruit. It is not probable that the mites would ever kill a tree though they might 

 so \\-eaken it that it would succumb to a very severe winter. It can, however, safely 

 be said that on. fruit trees this is at present much the most destructive of the Red 

 Spider type of mites in Ontario. 



