62 
FIRST ANNUAL REPORT OF THE 
manifestly be produced on similar principles. And, as we have seen in the case of the 
larva of the common Oyster-shell Bark-louse, the powdery bloom and the cottony floss, 
spoken of above, are met with at the very same time and in the very same insect; both 
of them proceeding, not from the mouth nor even from the tail, but from the general 
surface of the body. 
It is scarcely worth while, however, to argue such points as these with a writer, who 
is actually so ill-informed as to assert that “ everybody knows that the silk spun by in¬ 
sects is exuded through the mouth.” (Dr. Packard's Paper , p. 214). It is very true that 
it is so in the case of caterpillars, &c.; but in the case of the Ant-lions ( Myrmeleon ), the 
Caddice-flies (Phryganea), the Lacewing-flies ( Ohrysopa ), and probably of all true Neu- 
roptera, as distinguished from the Pseudo-neuroptera, everybody knows, or ought to 
know, that it is “ exuded,” not from the mouth, but from the tail.* Moreover, all the 
spiders without exception — which group of Articulate Animals Dr. Packard, in com¬ 
mon with the school to which he belongs, classifies as Insects — also spin from spinner¬ 
ets placed, not in their mouths, but in their tails. Yet, because this writer had happened 
perhaps, once or twice in his life, to see a caterpillar spin from its mouth, he jumps to 
the conclusion — with the same propensity for sweeping generalizations that character¬ 
izes everything that he has published — that all insects without exception spin from the 
mouth! ! ! 
From the enormous rate at which all Plant-lice multiply, it is plain that, if there 
were no check upon the increase of this species, it would, in a few years’ time, destroy 
every apple-tree in South Illinois. But, in all probability, there does exist one such 
check, at all events. Right in the middle of a little colony of these Root-lice I discov¬ 
ered in November the pupa of what I am pretty sure is a Syrphus Fly ; and Mr. Riley, 
to whom I showed the specimen, told me that he had formerly found great numbers 
of the larva of the same species among the infested roots — that he had reared it to 
the pupa state — but that he could never succeed in breeding it to the winged state. 
Apparently, this is the same insect, which, in the Prairie Parmer of June 15th, 1867, 
that gentleman mentions as, “having been always found by him in conjunction with 
this Root-louse, though he had failed to breed it,” and which he there describes as 
“ a footless maggot five or six times as large as the Root-louse, and of a dirty yellow 
color, attenuated at both ends, the head being quite retractile ;” and which he after¬ 
wards pronounces to be “ doubtless the larva of a Cecidomyia, the same Family to 
which the Hessian Fly belongs,” and to “take some part, probably, in inducing the 
deformities of the roots.” But certainly the insect that I showed to Mr. Riley does 
not even belong to the same great group of the Two-winged Flies as the Gall-gnats 
(Cecidomyia), inasmuch as it has what is called a “ coarctate ” pupa; (see above, pp. 31-2;) 
and I feel pretty confident that it will prove to be the Cannibal appointed by Nature 
to prey upon these unruly root-feeders, and keep them within reasonable bounds. 
The Syrphus family, however, to which it apparently belongs, includes many genera, 
which, in the preparatory states, can scarcely be distinguished from each other, and 
some of which feed upon decaying animal and vegetable substances, (. Xylota , &c.,) 
while others (Syrphus, Scceva, Volucella, &e.,) are Cannibals and feed upon other insects. 
In any case, I hope before next summer is over, to solve the mystery definitively, by 
rearing the winged Fly from the pupa which I found. If, as I confidently anticipate, 
*See Kirby & Spence’s Introduction, letter 13th, end; letter 21st, near the end; Fitch, N. T. Rep. I. 
p. 79; Shinier Proc. Ent. Soc. Pint. I A 7 , p. 210. 
