SUMMER MEETING. 79 



it varied from fifteen to ninety-five per cent, in strength and was unsafe to use. 

 He had applied it to plum trees to drive off the curculio but it killed the trees 

 and did not affect the curculios. 



After a somewhat rambling discussion upon insecticides Prof. Cook said: 

 There is an entomological topic, that as the years go by, we need to know more 

 about, and for the last few years farmers and horticulturists have opened their 

 eyes to the importance of more information, owing to the ravages of a certain 

 group of insects known as plant lice. It was with the thought of securing to 

 this seciety the technical information needed in fighting this enemy that Mr. 

 G. W. Park, who will now address you, was invited to prepare a paper upon 

 the subject of 



PLANT LICE. 



Perhaps there is no order that supasses the Hemiptera in the number of 

 (individuals, and even the species are exceedingly numerous. The very names 

 by which they are commonly known, bugs and lice, excite detestable feelings, 

 and recall to the memory, especially of the house-wife, experiences or duties of 

 • a character anything but pleasant and agreeable. Members of this order 

 attack both animals and plants, but it is in those that infest the plants that 

 the horticultur st is especially interested. Squash bugs, chinch bugs, plant lice, 

 — all are names very suggestive to those interested in the culture of plants, 

 i either for fruit or flowers. 



Entomologists have divided the order Hemiptera into two sub-orders — 

 ■Heteroptera embracing the bugs, and Homoptera the lice. Under Homoptera 

 are four families of plant lice, as follows: Psyllidse or jumping plant lice, 

 Aphidae or true plant lice, Aleurodidae and Coccidae or bark lice. The family 

 Aphida?, embracing the true plant lice, has been superficially divided for con- 

 venience into two tribes — Myzoxylinae, including the Grape Phylloxera, woolly 

 Aphis and others ; and Aphidinae, which embraces the genus Aphis, or plant 

 lice feeding on soft tissue ; and Laclmus, which infest the trunk and branches 

 of trees and shrubs It is chiefly to the former, the genus Aphis, that these 

 notes will refer. 



The species under this genus are so numerous and their special characteristics 

 so little known, that no entomologist has, as yet, attempted to make a compre- 

 hensive list of them from a scientific standpoint. They infest hundreds of 

 plants and trees, and in most cases the lice found upon one kind of plant are 

 different from those found upon another — different in color, form or manners, 

 though possessing the same general characteristics. It was the belief of the 

 great Swedish naturalist, Linnaeus, more than a century ago, that every plant 

 supported adistinct species of Aphis; and up till the present time this opinion, 

 as a rule, is concurred in by most scientists who have given this matter any 

 thought or consideration. Under these circumstances it is found convenient to 

 denominate as well as distinguish the species by the plant upon which the insect 

 is discovered. If upon the apple tree it is called Aphis mali; upon the plum, 

 Aphis prunifoliae; upon the rose, Aphis rosas. But this superficial system of 

 ■classification will not hold good in all cases, as almost any lady who cultivates 

 house plants knows to her sorrow. The same Aphis that troubles the fancy 

 Pelargonium will also work upon the Abutilon, the Achyranthus or the Calla. 

 A single individual of the greenhouse Aphis introduced into a window-full of 

 clean plants will soon infest all plants subject to Aphis, no matter upon which 

 of these the insect was first placed. It is true, however, that even the Aphis 



