80 



FIFTH ANNUAL REPORT 



least two brools of this Apple-tree Bark-louse ea^h year, and, though 

 he was evidently in error, so far as his own particular State (Massa- 

 chusetts) was concerned, and has been severely berated for the state- 

 ment by subsequent writers, yet it finally appears that his language is 

 not so very wide of the mark ! 



TRUE NATURE OF THE SCALE, WITH AUDITIOXAL PHYSIOLOGICAL FACTS. 



Not to repeat the views formerly entertained by Mr. Walsh, Mr. 

 Shimer and myseU, as to the nature of the scale, it is only necessary 



to state that my own opinion, that it is a secre- 

 tion analogous to that which is so generally 

 characteristic of the Ilomoptera^ has now be- 

 come a conviction, and is fully supported by 

 the study of this and allied species. If we 

 look at the common "Mealy Bug," {Coccus 

 adonidum Linn.), and take notice how the 

 mealy matter is secreted from the general 

 spores of the body, but more especially irom 

 the sides and around the anus, and then ima- 

 gine this secretion to be more attenuated and 

 more glutinous, and to harden and thicken at the periphery, so as to 

 confine the louse, and cause it to add more and more behind, as it 

 requires more room, we shall get a very good conception of the man- 

 ner in which our Birk-louse scale is formed. 



The newly hatched louse (Rep. 1, Fig. 2, ^) is oblong-oval, 0.01 

 inch long, rather more than half as wide, and one-fourth as thick. It 

 has antennae in wiiich may ordinarily be traced 7 joints ;* legs having 

 a short, one-jointed tarsus, a more or less distinct, but soft claw, and, 

 among other hairs, four at tip, which are knobbed, the upper pair 

 somewhat longer than the lower. The end of the body is bilobed, 

 and furnished with two long hairs or setaB. Except a deep yellow 

 spot near eacii end, the color is yellowish- white. 



As soon as fixed, there exudes, from the surface of its body, a 

 white waxy powder, which at first is seen in the form of threads, 

 (Rep. 1, Fig. 3, 5), but soon becomes homogeneous. In the formation 

 of this scale I have seen, in this species, quite coarse filaments ex- 

 tending on to the twigs, and in other species I have seen a waxy pre- 

 cipitation, covering the twig for some distance from the insect. This 

 secretion is easily rubbed off or dissolved in alcohol or ether, but if 

 undisturbed, forms a thin fibre on the thickening skin covering. In 

 a few days the first molt takes place, not as in the ordinary manner 

 with insects, by a series of contractions and extensions which work 

 the old skin to the end of the body from which it is finally freed, but 



*The 8-jointe(lfl-Ure in my first Report is evidently a mistake, cansel l)y tlie u-;e of too feeble 

 resolving power, aB J have uot been able to detect 8 joints in specimens examined more carefully sinct • 



