228 TRANSACTIONS OF THE ILLINOIS 



louse. Would either of us be justifiable in charging neighbor Jones with robbing our 

 corn crib, simply because he passed that way every night, from his daily labors. The 

 crib may have been relieved of all its contents, but still neighbor Jones is innocent 

 before the law until proven guilty. We know that the apple bark louse does spread 

 from tree to tree, but reasoning in the same way we ought to hold the birds innocent 

 unless proven guilty. 



But if we conclude to lay the charge upon them by the method of exclusion — not 

 finding any other method by which the bark louse can be distributed ; we must first 

 by close observation exhaust all other methods. This accomplished, we may then, with 

 some show of justice, bring so grave a charge against the birds. 



Reasoning in this manner, I commenced my observations in the early spring, in the 

 orchards of Mt. Carroll Seminary grounds, and neighboring farms, where I had ample 

 material for the most complete research ; making notes as I proceeded, the essential 

 parts of which I herewith submit for your consideration. 



May 15th. — The apple trees are in full bloom. Within the past few days, my attention 

 has been called by V. Armour, Esq., to a wild red plum tree, which he calls " Missouri 

 Plum," on which are great numbers of this identical "bark louse" (Lepidosaphes 

 (aspidiotus) conchiformis.) They appear, chiefly, to be last years' scales, yet very few 

 of them have sound eggs ; they have been despoiled by some parasite. 



I also found this same unmistakable "bark louse" quite abundant on the "Moun- 

 tain Ash," (Pyrus Americana) in a neighbor's garden ; the eggs have been injured in a 

 similar manner. 



In these cases the affected trees, Plum and Ash stood close to apple trees covered 

 with bark lice scales. This is very interesting, as proving to my mind that the "apple 

 bark louse," is capable of living on trees, not only of different genera, but also on 

 those of widely different families. After seeing this we can readily appreciate the cor- 

 rectness of the declarations of Mr. Curtis, that this insect is identical with the coccus 

 arbour m Unearies,GeSry, of the Elm — a thing which appears inconsistent with the 

 modern notions of the habits of plant lice. 



May 24th. — During the past few days we have had very fine, mild weather, and I have 

 occasionally observed young bark lice crawling on the trees. A few of them I find here 

 and there on the trees already, in the form of the new little scale. 



At 3 P. M., I observe their rate of motion by time and instrumental measure. The 

 distance traveled per minute was from six to eight-tenths of an inch, in a straight line, 

 which gives three and a half feet per hour, or eighty-four feet in twenty-nine hours. 



The eggs beneath the scale are not hatched ; so it appears that they hatch out irregu- 

 larly, this year, and leave the parent scale immediately. This may be accounted for by 

 early fine weather. Last year it was too cold for them to hatch until quite late, in con- 

 sequence of which, they nearly all came out together, and in some instances remained 

 some time under the scale, after hatching as reported by Mr. Riley to the State Society. 



May 25th. — I saw the first young Acarus Malus of the season. 



May 26th. — Rainy ; saw no bark lice. 



May 27th. — Fair and windy. Bark lice abundant on the trees. Got down on my 

 knees, and carefully examined the ground around under the trees, and between them, at 

 various places in the orchard, with a leus. I saw many bark lice all over ; especially 

 more numerous under the trees ; six and more, sometimes, immediately under one field 

 of the lens. Everywhere in the orchard, even half way between the trees, I could find 



