222 INSECTS INJURIOUS TO VEGETATION. 



of the trees with a brush, and as high as practicable, so as to 

 cover the whole surface, and fill all the cracks in the bark. 

 The proper time for washing over the trees is in the early part 

 of June, when the insects are young and tender. These in- 

 sects may also be killed by using in the same way a solution 

 of two pounds of potash in seven quarts of water, or a pickle 

 consisting of a quart of common salt in two gallons of water. 

 There has been found on the apple and pear tree another 

 kind of bark-louse, which differs from the foregoing in many 

 important particulars, and approaches nearest to a species 

 inhabiting the aspen in Sweden, of which a description has 

 been given by Dalman in the " Transactions of the Royal 

 Academy of Sciences of Stockholm," * for the year 1825, under 

 the name of Coccus cryptogamus. This species is of the kind 

 in which the body of the female is not large enough to cover 

 her eggs, for the protection whereof another provision is made, 

 consisting, in this species, of a kind of membranous shell, of 

 the color and consistence almost of paper. In the autumn 

 and throughout the winter, these insects are seen in a dormant 

 state, and of two different forms and sizes on the bark of the 

 trees. The larger ones measure less than a tenth of an inch 

 in length, and have the form of a common oyster shell, being 

 broad at the hinder extremity, but tapering towards the other, 

 which is surmounted by a little oval brownish scale. The 

 small ones, which are not much more than half the length of 

 the others, are of a very long oval shape, or almost four sided 

 with the ends rounded; and one extremity is covered by a 

 minute oval dark colored scale. These little shell-like bodies 

 are clustered together in great numbers, are of a white color 

 and membranous texture, and serve as cocoons to shelter the 

 insects while they are undergoing their transformations. The 

 large ones are the pupa-cases or cocoons of the female, beneath 

 which the eggs are laid; and the small ones are the cases of 

 the males, and differ from those of the females not only in 

 size and shape, but also in being of a purer white color, and 

 in having an elevated ridge passing down the middle. The 



* Kongl. Vetenskaps Academ. Nya Handlingar. 



