HEMIPTERA. 203 



brush, and as high as practicable, so as to cover the whole sur- 

 face, 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 in- 

 sects are young and tender. These insects 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 Dal- 

 man in the " Transactions of the Royal Academy of Sciences of 

 Stockholm", * for the year 1825, under the name of Coccus cryp- 

 togamus. 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 clus- 

 tered together in great numbers, are of a white color and membra- 

 nous 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 pass- 

 ing down the middle. The minute oval dark-colored scales on 

 one of the ends of these white cases are the skins of the lice while 



* Kongl. Vetenskaps Academ. Nya Handlingar. 



