ENTOMOLOGIST AND BOTANIST. 



359 



the roots, may have been gradually acquired. We be- 

 lieve a parallel case presents itself in our Apple Root- 

 louse (Eriosoma pxjri, Fitch) and the WooUy Aphis, or 

 so-called "American Blight" {Eriosoma lanigera, 

 Hausm). It is conceded on almost all sides* that the 

 last insect was imported into Europe from this country, 

 and there is now every reason to believe that the two 

 insects are iudentical, or that at furthest they can only 

 be considered as varieties of one species. Yet while in 

 this country our root-louse is very injurious in the 

 West, and only exceptionally found on the limbs 

 above ground (though more often so found in the 

 Eastern States); all authors that we are acquainted 

 with have spoken of it as occurring solely on the limbs 

 in Europe; though M. Lichtenstein informs us that he 

 has found it on the roots there also, and that in those 

 cases it caused just such swellings of the roots as our 

 root-louse does here. We know in St. Louis of an old 

 apple-tree, standing in a yard where the ground is 

 trodden hard , the limbs of which have been for the past 

 three years more or less affected with this insect, though 

 none can be found on the roots. But where the ground 

 is more porous, and not so closely pressed to the roots, 

 it seldom occurs on the branches, but often on the roots, 

 even in the immediate neighborhood. Upon the closest 

 examination we cannot find the slightest difference be- 

 tween the root and branch-inhabiting lice, and no doubt 

 their habitat is governed somewhat by the character of 

 the soil, though in this country their normal habit is to 

 attack the roots, and to appear above ground only occa- 

 sionally in the fall. 



Secondly, we have proved, by transferring on to 

 roots the young grape-lice hatched from galls, and by 

 successfully feeding them on those roots, that our 

 smooth gall-inhabiting type gives birth to the tubercled 

 root-inhabiting type; and we have discovered that our 

 gall insects take to the roots in the fall, on which they 

 cause the same cankerous spots and swellings as does 

 the vastatiix of Europe, and on which they evidently 

 lin)ernate just as vastatrix is known to do. 



Thirdly, although in the gall-inhabiting type, in both 

 countries, the tarsus seems to be one-jointed, yet in 

 the root inhabiting type it is really two-jointed ; for 

 though the basal joint is small, and not visible from 

 above, it is plainly visible from the side or from below 

 (See Fig. 219, h). We have here what certain speculative 

 entomologists would consider an excellent illustration 

 of the Inferiority of Coccidoe compared with the Aphi- 

 dic, namely, a true Aphidian, exhibiting in its larval 

 and agamic stage the one-jointed tarsus of a Coccid, and 

 only showing the two-jointed tarsus of its family in the 

 more perfected tubercled form, and in the winged state. 

 And this Coccid-afiinity in the less perfect gall-producing 

 state is sometimes carried still farther, as we have often 

 been unable to discern but a single claw to the tarsi of 

 some of the young gall-inhabiting individuals. 



Fourthly , the fact that M. Signoret, who alone has 

 compared actual specimens from both countries, de- 

 cides them to be identical, would sufficiently indicate 

 that the difference noticeable in the form depends on 

 the observer, and on the stage of growth at which ob- 

 servations are made. 



It was the one-jointed tarsus in the gall insect which 

 no doubt in part led Dr. Shimer to propose a new 



•M. Eudes-Deslongchamps and M. Blot are the only 

 authors, according to Amyot aud Serville, who belitve it is 

 iudigenous to Europe. 



family for it , and it was this character — coupled with 

 the facts that it is oviparous , that it does not secrete 

 any sugary or flocculent substance (as do most gall-in- 

 habiting Plant-lice), and that the young forsake the gall 

 and scatter over the leaves as soon as hatched— which 

 led Mr. Walsh to consider it as an anomalous and aber- 

 rant Coccid. The genus Phylloxtra, seems also, accord- 

 ing to Westwood, to have been doubtingly introduced 

 into this family by Curtis in his Guide. We have al- 

 ready shown that, in the root-inhabiting form, the two 

 joints of the tarsus are plainly to be seen; aud Dr. 

 Shimer himself admits* that, in the winged insect which 

 he found in galls, he noticed a constriction on the under 

 side of the tarsus, though he is unwilling to allow that 

 it was a joint, because there was no motion. But even 

 if the 2-jointed character of the more perfect louse were 

 not demonstrated, all the other characters are so un- 

 mistakably Aphidian that there is, we think, no war- 

 rant in making a new family. In such degraded insects, 

 where the antennal joints are so variable, we might 

 naturally expect to find variation in the joints of the 

 legs. The more familiar we become with the biological 

 secrets of Nature, the more do we find, not only species 

 but genera, and even families, approaching each other 

 through modifications found in individuals; and these 

 aberrant gall-lice only help to give us a better idea of 

 the close connection between the Coccid^ and APHiD.ffi;. 

 Our Phylloxera brings the two families close together, 

 by its affinities on the one side with Ckermes of Liumjeus, 

 which, though looked upon as a Coccid by Ratzeburg, 

 is generally considered an Aphidian, and on the other 

 with the Coccidan genus Dactylopiua which contains 

 Linnseus's Coccus adofiidum. The oviparous nature ol 

 these gall-lice will also have less significance when we 

 reflect that there is a sort of gradation in this process, 

 and that many Plant-lice which are considered vivi- 

 parous or ovoviparous do in reality bring forth their 

 young enveloped in a more or less distinct egg-like film 

 or covering, from which they have to free themselves 

 by a process analogous to that of hatching. This has 

 not only been observed by Curtis, in the case of an 

 Aphis found on the turnip,t but by Dr. Wm . Manlius 

 Smith, of Manlius, N. Y.,{ in the case of Pemphigus; 

 and we have, the present year, assured ourselves of the 

 accuracy of Dr. Manlius's observation as to Pemphigus, 

 and witnessed the same thing in Eriosoma, namely in 

 E. pyri. Fitch. In this last case the newly deposited 

 louse [or egg] remains motionless for a considerable 

 time; and the covering, after the young louse has ex- 

 tricated itself from it, may be as distinctly seen attached 

 to the end of its body as the covering or egg-shell of our 

 Grape gall-louse, and was figured by Fitch, who mis- 

 took it for the cotton-like matter, which, however, is 

 not secreted till the louse fastens itself and begins to 

 gi'ow.§ Moreover those Aphidiaus which are viviparous 

 through the spi-ing .and summer months , generally lay 

 eggs in the fall ; aud though agamous and viviparous 

 multiplication can be prolonged by submitting the lice 

 to a continued artiflcally wai-m temperature, there is 

 doubtless a limit to this prolongation; and it may be 

 laid down as a rule that, with most Aphidians, the rf" 

 element and the production of eggs are, at some time or 

 other, indispensable to the continuance of the species. 



^Characters of a Supposed Neio Family, p. 3. 



IFarm Insecls, p. 65. 

 Auctore Walsh, P. E. S. P. VI, p. 282, note. 

 N. Y. Kep. I, p. 9. 



