12 FIRST ANNUAL REPORT OF 



gravid, until it is now a mere atom at the anterior or narrow end of 

 the scale, in a few days scarcely to be noticed at all. 



The oyster-shell bark-louse produces but one brood annually, and 

 these eggs, therefore, remain under the scales for more than nine 

 months of the year, subjected alike to the continuous warmth of the 

 fall months, and to the severe frosts of winter; freezing and thawing 

 again and again, without their vitality being in the least impaired. In 

 order to show the conclusions which I came to, after the above obser- 

 vations, I will, in a measure repeat them. 



All writers on this Bark-louse, copying after Fitch and others, tell 

 you that the scale you see on your trees is the gravid body of the 

 female insect. Now, though for aught I know the body proper of the 

 female may, in some Coccidan species, extend and cover the eggs she 

 deposits, it is no such thing in this instance ; and I am prepared to 

 affirm that the scale is no more the insect's gravid body than is the 

 empty muscle shell the distended outer membrane of the muscle, or 

 the oyster shell that of the oyster. 



How this scale is formed I do not profess to have discovered. 

 With regard to our native white species, already referred to (p. 7), Mr. 

 Walsh, in the Practical Entomologist for December last, refutes Har- 

 ris's theory, namely, that it is formed in the same way as the down 

 which exudes from other lice, and shows, with some plausibility, that 

 it may consist of the cast-off skins of the insect. Now, in my own 

 humble opinion, with the imported species under consideration, I am 

 inclined to uphold Harris, for the following reasons : besides the fine 

 waxy filaments which it secretes when becoming fixed, I have found 

 that, even before these are thrown out, it is covered with a fine, white 

 bloom, proving that it can and does secrete from the general surface ; 

 having carefully lifted the scale, every day during the growth of 

 the third portion referred to, the louse has invariably been found in 

 the same shape and condition, without apparent connection with it, 

 while the scale, to all appearances, actually increases in bulk during 

 the time the eggs are being deposited. Furthermore, the exuviae of 

 such a tiny insect would be infinitely thinner and more delicate than 

 is the scale, and as the insections, especially of the verter, are always 

 plainly visible with a glass, in the louse, we should expect to see them 

 in the scale, which is, however, perfectly smooth. Again, the louse 

 is of the same color throughout its growth, while at one time the 

 three parts of the scale are perceptibly different in this respect. 

 Moreover, Reaumur long ago (Memoires, torn. IV., p. 26) observed a 

 species occurring on the peach in France to cast its skin in flakes, 

 much in the manner as many of our Dipterous and HymenopteTOus 

 larvos are known to do ; while he also described a species (pp. 64, 65, 

 ibid.) occuring on the vine, which covered its eggs with a white, 

 gummy, cottony secretion; and Mr. Walsh himself, in the February 

 number of the little monthly already referred to, p. 57, speaking of a 

 species occurring on the under surface of the leaves of the Olea 



