32 



THE PRACTICAL ENTOMOLOGIST. 



the autumn bj the insect, like a cocoon, of some 

 white material, its dried up and pale-brown body being 

 attached to one end of it — is milk-white, so as to be in 

 strong contrast with the bark — much more flattened than 

 in the Oyster-shell species — and the eggs under the scale, 

 instead of being milk-white, are pink or lake-red all 

 through the winter. These eggs hatch out about as the 

 preceding. The species was described, but not named, 

 by Harris; and, just as he states, there are scales of two 

 distinct shapes promiscuously intermixed, one short-oval* 

 and the other very similar to that of the Oyster-shell 

 species, as shown in the above figure at A and B. He is 

 mistaken, however, in supposing that the oval scales are 

 those of the male insect; for these, as well as the elong- 

 ate or oyster-shaped ones, have a parcel of eggs under 

 each of them ; neither is it true, as he asserts, that the 

 oval scales are only about half as long as the oyster- 

 shaped ones; for on the average they are a trifle longer, 

 though the range of variation is very considerable. Sin- 

 gularly enough, he says nothing of the remarkable red 

 color of the eggs. As to the diflerence in the shape of the 

 scales, as both kinds from their containing eggs under 

 them must be those of females, I suppose we have here 

 another case of what is called "Dimorphism" by modern 

 Naturalists, as with the two kinds of females found among 

 the Plant-lice. In any case the paragraph in Harris, (pp. 

 255 — 6,) which has been copied from Caiman's account of 

 a Swedish kind of Bark-louse found on the aspen, (Coccus 

 cryptogamus,) can have no application whatever to this 

 species. 



I doubt very much Harris's theory — which appears to 

 be founded merely upon the analogy, now shown to be al- 

 together erroneous, with Dalman's Swedish species of 

 Bark-louse — that the scales of this American species are 

 not composed of the dried body of the female, but "in the 

 same way as the down which exudes from the bodies of 

 other bark-lice." In the middle of November there may 

 often be seen on such twigs as are infested by these scales, 

 very numerous cast skins of the immature insects, not 

 tightly affixed to the bark like the true egg-bearing scales, 

 but loose like the cast skins of plant-lice. These cast 

 skins are milk-white, oblong-oval, about 2i or 3 times as 

 long as wide, and show at one end of each precisely the 

 same oval, pale-brown scale that appears at one end of 

 the true egg-hearing scale of either shape. This pale- 

 brown scale is divided, by faint cross-lines, into segments 

 like the bodies of almost all insects. I infer that it is the 

 cast skin of the back of the insect, and that the rest of the 

 cast skin, which is white and devoid of cross-lines, is that 

 of the inflated and elongated venter. What confirms me 

 in this opinion is, that frequently the pale-brown scales 

 may be met with without any white appendage behind 

 them. Hence, I conclude, from analogy, that the true 

 egg-bearing scale, also, whether the short-oval kind (A) 

 or the oyster-shaped kind (B), is composed of the body of 

 the female bark-louse, as in the imported species, and 

 not, as Harris believed, spun or otherwise constructed by 

 the insect. I have forwarded specimens of all these mat- 

 ters to the Entomological Society for the satisfaction of 

 the incredulous. The whole case aflbrds an instructive 

 example of how the best of us are sometimes deceived by 

 false analogies, and jump too hastily to erroneous conclu- 

 sions. But after all, this is a matter of no practical im- 

 portance, though it is of considerable scientific interest. 

 It only remains to add that when, as sometimes hap- 

 pens, these two kinds of Bark-lice are intermixed on the 

 same tree, the oyster-shaped scales (B) of Harris's Bark- 

 louse may be readily distinguished from those of the Im- 

 ported species by their being milk-white, instead of the 

 color of the bark, and by the eggs under them being pink 

 instead of milk-white. We have here another instructive 

 example of the difl'eronce between the destructive powers 

 of Imported and Native American Insects. Myriads of 

 trees in the United States have been killed by the Im- 

 ported Bark-louse of the Apple-tree; and yet our Native 

 Species, which infests the same apple-tree, has never yet 

 been known to kill a single tree. 



Soda-wash and other alkaline watery infusions, to be 

 of any service, must be applied after the young bark-lice 

 have hatched, or some time in June. The eggs are so ef- 

 fectually protected by the scale, that no watery infusion 



*Harris says, "of a very long oval shape or almost four- 

 sided;" but "long" is evidently a clerical error for "short." 

 (See Inj. Ins. p. 256.) 



can reach them, though, as I have demonstrated by care- 

 ful experiments, a thin coat of kerosene put on with a 

 brush, any time in the dead of the year, will kill them 

 every one. The reason is obvious. Nature has made the 

 scales rain-tight, but, as we have no showers of oil, she 

 has not thought it necessary to make them oil-tight. 

 Probably benzine, as it evaporates much more quickly, 

 would be preferable to kerosene, or perhaps either might 

 bear to be diluted with water. I observed that about one- 

 aixth of the limbs that I painted with pure kerosene died, 

 and that in every case these were such limbs as were 

 most badly infested by the Bark-louse. Possibly these 

 would have died in any event, or, as I rather inl'er, being 

 greatly weakened by the insect they might have had the 

 finishing stroke given them by the kerosene. 



I do not believe that either Soda-wash or Kerosene oil 

 will kill egg or larva, excei)t such as it actually touches. 

 People are perpetually reasoning upon the assumption, 

 that such substances are immediately taken into the cir- 

 culation of the washed or oiled plant; as if plants, like the 

 higher animals, had a complete circulatory system of 

 veins and arteries, whereas every Botanist knows that it 

 is no such thing. Hence, if Bark-lice had the habit of 

 spreading themselves evenly over a whole tree, aftur the 

 manner of the winged Plant-lice, it would be very diffi- 

 cult to fight them ; for in that case we should have to ap- 

 ply the necessary wash or oil to every limb and twig. 

 Fortunately, however, for us the female bark-louse is 

 wingless, and the only way in which she can, as a gene- 

 ral rule, pass from one tree to another, is by adTiering to 

 the feet of some bird as it flies from one tree to another. 

 I have long observed that when a tree first begins to be 

 attacked by bark-lice, it is only particular limbs and 

 branches that are at first infected, and that these will be 

 swarming while the rest of the tree will be free from lice. 

 And I have further observed that it is the lower horizon- 

 tal limbs and branches, or such as birds would most na- 

 turally perch on, that are first attacked. If neglected, 

 however, the insect will gradually spread over the whole 

 tree in the course of a. few years, when, in the case of the 

 Imported Bark-louse, the result is sure and speedy death. 

 Hence, it will be seen that, to check the operations of the 

 Bark-louse in its earlier stages, it is not necessary to operate 

 on the whole tree, but only on such limbs as are actually 

 infested. 



I have found that Bark-lice may be greatly checked, 

 by placing upon the infested tree, a dozen or two of the 

 Ladybirds figured in the mar- 

 gin. The one to the left — the aif^UPtfi T 

 Twice-stabbed Ladybird ( ^^"''>fl ff ' itfF i BB w 

 hrorus bivulnerus) may be ta-^'*wii"li™i~''-t 

 ken on forest-trees in consider 

 able numbers by beating thi 

 boughs into an inverted um- Colors — black Colors, pink 

 brella. The one to the right— ^nd red. and black, 



the spotted Ladybird (Hippo- 



damia macutata) — may be taken abundantly on herbage 

 with a common "sweeping-net," which is simply a bag 

 of strong cloth sewn upon a hoop of strong iron wire and 

 attached to a stout statf. 



As to your queries under this head, I assume that your 

 painting your trees with soda-wash did no good what- 

 ever, because it was done, as you yourself say, in the fall, 

 when the insect was in the egg-state, and sheltered un- 

 der the protecting scale. You saw no living insects the 

 following summer, because they are then very minute, 

 almost motionless, and hard to perceive with the naked 

 eye. But when the new scale w.is formed on Sept. 20th, 

 then you saw them. Most certainly the female Bark- 

 louse never descends to the earth. On my own trees I 

 never find any Bark-lice on the trunks, but then the 

 trunks of my trees are scaly and rough, and yours having 

 been treated with soda-wash wouhi probably be smooth. 

 I doubt the fact of the Scale appearing on your trunks 

 any considerable time before it appeared on the branches. 

 Your supposition that the eggs of Apjile-tree Bark-lice 

 could be de]>osited " in June or July " is of course incor- 

 rect, as has been shown above. 



3rd. The large Blister-beetle, that eats your pears, is in 

 all probability the Lytta Sai/i of LeConte. Say first de- 

 scribed it, supposing it to be a mere variety of his Lytta 

 anea, whereas it is in reality a distinct species. After Le- 

 Conte had established it as a distinct species, and named 

 it after Say, ",S'aj/e,'' Pitch, sujiposing he had got hold of 

 an undescribtd species, named and described ii over 



