'204 TRANSACTIONS OF THE ILLINOIS 



weather is equally surprising ; and the universal diffusion of such myriads, 

 soon after a thunder storm, has led, as with the black caterpillars, to the 

 vulgar error of their having fallen from the clouds. ' ' He thinks it probable 

 that electricity also assists in their rapid and sudden development, some- 

 times observed. It is proper to state that Dickson, in his " Practical 

 Agriculture," remarks that, "In such summers as are dry, beans are fre- 

 quently liable to be much injured by the attacks of the Black Fly, or what 

 is often termed the Dolphin, the whole field in particular cases being in 

 danger of being destroyed in the course of a few days." Black fly, 

 black dolphin and collier are terms applied in England to a variety of the 

 Bean Aphis. It is not stated here that it is the universal increase of these 

 insects that renders the beans more liable to destruction in dry than wet 

 seasons ; it is more than probable the weakened vitality, caused by want 

 of moisture, has much to do with it. 



One instance has been recorded of a remarkable migration of these 

 insects, which occurred in Belgium. M. Morren, who records the fact, 

 says that the winter of 1833-4 was very mild, and the summer following 

 very hot and dry. That in September the plant-lice ( Aphis persicce) sud- 

 denly appeared in immense numbers, resembling the locust emigrations, 

 the flying hordes even obscuring the sun, and entirely covering the sides 

 of the house where they alighted. It is stated by another authority that 

 they were carried thither by a hurricane. 



The fact that ants attend the species which give forth a saccharine 

 fluid from honey-tubes, for the purpose of obtaining this food, and the 

 fact that the lice permit their attention and caresses without objection, 

 are too well known to need further mention. 



As a rule, the remedies applicable to one species are equally applica- 

 ble to another of similar habits, where the one is as easy of access as the 

 other. But the measures so far suggested apply almost exclusively to spe- 

 cies that operate on the surface of the foliage, branches, trunk or roots, 

 and not to those which inclose themselves in galls ; fortunately, the latter 

 are not often injurious to growth, though giving the tree or plant they 

 infest an unsightly appearance. The attention which has lately been 

 called to the Grape Phylloxera, in this country and France, especially the 

 latter, has brought to light many facts with reference to remedial and pre- 

 ventive measures applicable to root-lice, of great value. I therefore give 

 here a resutne of the results of the experiments tried under the supervision 

 of the Academy of Sciences of France, upon the Phylloxera of the Grape, 

 copied from Nature, No. 375, January 4, 1877 : 



" Some time ago we published in our columns a short account of the 

 results of the investigations of various scientific men in France into the 

 nature of the Phylloxera — that terrible scourge which is committing such 

 wide-spread ravages among the French vineyards. Latterly we have 

 received some reports communicated to the French Academy of Sciences, 

 dealing with the attempts which have been made during the last three or 

 four years to arrest the mischief done by the insect, and ultimately to 

 destroy it altogether, by means of some potent drug. It is obvious that 

 the remedy to be employed must possess two qualities at starting, viz.. 



