74 FIFTH ANNUAL REPOKT 



tory of the little animal which causes what is often called "scurvy" 

 on apple-trees. 



ITS OCCURRENCE IN MISSOURI. 



From numerous facts stated, and from experiments made, in 1868, 1 

 had every reason to suppose that this insect could not thrive at any 

 point south of St. Louis, and that it had, up to that time, not yet been 

 introduced into the State. But, alas ! both these cherished notions have 

 been dispelled like "the baseless fabric" of a vision, and I am very forci- 

 bly reminded of the uncertainty of analogic reasoning, and how neces- 

 sarily imperfect and partial human knowledge must always be ! The 

 conclusions drawn from the facts at hand in 1868 were : 1st, that this 

 Oyster-shell Bark-louse did not yet occur in the northern part of the 

 State, though quite capable of existing there ; 2nd, that by care and 

 caution on the part of orchardists in the more northern counties, its 

 introduction could very easily be prevented; 3rd, that it could not 

 thrive in the southern half of the State. The first conclusion, from all 

 I have been able to learn since, was fully warranted ; for, except in the 

 latitudinally opposite localities presently to be specified, I have not 

 met with or heard of it. So truly indeed is this the case that specimens 

 for study were necessarily obtained from these localities, or from the 

 more northern parts of Illinois, and the observations here recorded 

 were, consequently, made under difficulties. The soundness of the 

 second conclusion we have been abundantly able to test, for the worst 

 fears that the pest might be introduced have been realized. Just as 

 might have been expected, also, it has gained a footing in the extreme 

 northeast corner of the State — the point of greatest proximity to the 

 infested sections of Illinois and Iowa. 



In the spring of 1870, Mr. B. P. Hanan, of Luray, Clark county, 

 sent me some Sweet June apple-twigs that were completely covered 

 with the scales of this Bark-louse, and the eggs underneath the scales 

 were plump and healthy. The twig's were taken from the orchard of 

 Dr. Wm. H. Martin, of Kahoka in that county, and I quote part of Mr. 

 Hanan's letter which accompanied them : 



"This tree is rather badly infested, and I find by examination that 

 they (the insects) are spreading slightly on to the nearest trees around 

 it. Will they spread from one orchard to another, one or two miles 

 distant? I saved my orchard from the native White Bark-louse by 

 sending you specimens of them and of their foes, and by learning from 

 you what to do to destroy the lice. I took your advice, encouraged 

 the ladybirds, and they cleared my trees of the lice. If your advice 

 in this case shall accomplish as much for my friend Dr. Martin, the 

 object of this communication will have been accomplished." 



At my suggestion, the tree was cut down, and other measures 

 taken to eradicate the evil on trees adjoining ; and, from correspond- 

 ence, I was finally led to believe that it had actually been eradicated. 



