130 
on the unfolding leaves of the growing tips. This accounts for the 
unequal distribution of the galls on the leaves of the plants; they 
are very rarely uniformly abundant on the whole leafage, loung 
trees seem to be more liable to be galled than older ones, and 
plants which are heavily shaded or otherwise unfavorably situated 
seem to prove more attractive to the mites than those which get a 
due amount of sunlight and rain. Several hundred of the galls 
may occur on a single leaf, and sometimes there are few leaves on 
a plant which are not galled. 
THE MITES. 
Among the many strange forms of Acarina, none have proved 
more puzzling to entomologists than the members of the genus 
Pliytoptus. In this case, the extremely small size of the animals 
has been an additional hindrance to an understanding of their struc¬ 
ture, and, added to their abnormal form (abnormal even to the 
class in which they belong), has led to much confusion and un¬ 
certainty as to their relations to other mites. There seems, how¬ 
ever, to be no longer reason for doubting that Phytoptus is an adult 
mite, capable of laying eggs and reproducing its kind. I believe 
none of those who have considered Phytopti the larvae of other mites 
claim to have actually observed the transformation of one into the 
other, or, indeed, to have made anything like a careful and scientific 
demonstration of what they give as the genealogy of these mites; 
and as several competent observers have recently seen the ova, and 
one of them even the act of oviposition, we cannot longer withhold 
from Felix Dujardin the credit of having been right, when in 1851 
he claimed that he had seen ova within the body of Phytopti, and 
that they must therefore be adult mites, notwithstanding their having 
but two pairs of leg$. We may therefore define Phytoptus as a 
genus of mites with two pairs of legs composed of five articles each, 
and terminated by a claw and feather-like organ, as possessing a 
tubular rostrum, including a pair of slender maxillae, and with a 
long, transversely-striate abdomen, terminating in a protractile 
sucker. 
The minuteness of Phytopti is such that a microscope is neces¬ 
sary in studying them. They are invisible to the untrained eye,— 
and even after being searched out with a lens, can only be seen, 
with the closest scrutiny, as minute, .whitish specks. The length 
varies, in specimens I have seen, from .003 to .004 inch. The 
species differ so little, that quite a detailed description of one ap¬ 
plies equally well for all the members of the genus. They are 
cylindrical, semi-transparent, with a disportionately long abdomen, 
and very short cephalothorax. The latter constitutes not more than 
a fourth of the entire length of the mite, is smooth and shining, 
and continues forward without interruption into the rostrum. The 
rostrum is little else than a hollow snout, cut off squarely at the 
tip and slit open longitudinally below. In other mites a partial ros¬ 
trum is formed by the union of the bases of the mouth-parts with 
the labrum, the terminal (distal) part of the organs remaining free. 
In Phytoptus the fusion is carried further, and the chelipeds are 
lost in the rostrum. Apparent joints may sometimes be seen just 
