366 HENRY SHIMER, M. D. 



gradually during the summer, it must be a secretion of some kind from 

 the posterior end of the abdomen ; and as I was not able to detect any 

 excrement inside of this habitation at any time during the summer, I 

 believe it to be excrementitious matter, deposited in a semi-liquid state, 

 which, upon drying, is the impervious tenement of the insect. This 

 idea may appear ridiculous to many, that an insect should use its own 

 dung to patch its old cast-off garments and thus construct a comfortable 

 house. Instead of being absurd, however, it is an example of unparal- 

 leled economy. Neither is it without a partial example, for the larva 

 of Lema (crioceris) tn'h'neata Olivier (the Three-lined Leaf-beetle, see 

 Harria' Inj. Ins. p. 119,) which covers its back with its own dung to 

 protect it from the sun and injurious insects. 



But in this Apple Bark-louse we have one of the most wonderful 

 examples of the economy of nature — a naked insect anchored on the 

 limb of a tree, exposed to all the inclemency of the elements, too poor 

 to secure the labor of others more favored by the Goddess of Fortune, 

 doomed to remain fixed to the spot for life, without limbs to help it- 

 self, unable to rob some poor sheep of the fleecy covering on its back, 

 or to secure the products of a cotton-field : not provided with the silk 

 of the caterpillar, nor yet able to employ a weaver or tailor. In such 

 a deplorable condition it does not despair, but diligently uses the only 

 means at its command — its cast-off exuvia; and excrement, by which it 

 constructs a shelter that protects, not only itself, but also its eggs from 

 the sun and rains of summer, and the piercing blasts of winter, with 

 the thermometer 20^, 30°, and even 40*^ below zero. Truly, the works 

 of nature are infinitely variable, wonderful in their extremes, and re- 

 markable in adapting means to ends. 



July 7th. — Examined the Bark-louse microscopically. They are 

 easily separated from their scales. They present at this time a flat- 

 tened flask or jug-shaped appearance, in profile, obovate. The abdo- 

 men is very large, the sides crenate, the abdominal extremity with a 

 distinct notch, the segments plainly visible, the neck and head narrow. 

 Color yellow. A few short hairs are visible around the margin of the 

 abdomen. Is is motionless, appearing pupa-like, except in wanting 

 marks of developing legs and wings. Length .04, breadth .02 inch. 

 Concave beneath, convex above. At this time a few of them appear 

 to be dead and drying up, but mostly when crushed a reasonable (juan- 

 tity of liquid juice is seen. The accidental arrest of development in 

 this state has led some, erroneously, to think that these small scales are 

 male producing. 



