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freedom of linear growth and a peculiar and well-marked leaf. Well not uncom- 
monly when we find this same shaped leaf occurring in another genus, the species 
so leaved forsaking the habit of growth usual in the genus assumes more or less 
that of the ivy. Look for instance at the ivy-leaved Campanula, the ivy-leaved 
Foodflax, the ivy-leaved Geranium. Here it would seem that the shape of the 
leaf or something in connection with that shape has induced the growth of all these 
very different plants more or less in the same direction. And we cannot but 
think that something similar is at the bottom of many cases of likeness in the 
animal world, and to be satisfied with the application of such a term as mimicry 
is unphilosophical, since at the best it can be but a preservative agent, and does » 
not touch that deeper question, the origin and cause of the likeness. 
But to turn to more practical questions. These internal feeders, at least 
those of them that infest trees, are necessarily injurious, but while some, as 
Bembeciformis, Apiformis, Tipuliformis and Sphegiformis, attack healthy and 
vigorous trees, others, as Myopiformis, Culiciformis, and Cynipiformis, prefer 
those that are diseased or injured. As has been said, the moths themselves are 
seldom seen, and are consequently scarce insects in collections. The only species 
T have noticed on the wing in the wild state have been Cynipiformis, Ichneumoni- 
formis, and Sphegiformis, but when the habits of the larve are known, many of 
the species, even of those usually reckoned uncommon, may be obtained in 
abundance and without difficulty. All the smaller species have a tuft of bristles 
at the end of the body. This is an interesting anatomical feature, for in some 
specimens of Culiciformis that I bred I noticed they had the power of expanding 
it at pleasure. This tuft consists of three sets of bristles, a middle set which are 
horizontal, and a set each side which in repose are vertical and look downwards. 
It is in these side portions the movement resides, the insect being able to raise 
them and thus increase its horizontal superficies, an obvious advantage for pur- 
poses of flight and hovering. Probably all the species provided with this tail, so 
to speak, have the same control over it. I will now say a few words about each of 
the species that occur here. 
Myopiformis is widely distributed but not abundant. The larva lives in the 
trunks of the apple trees, mining the bark. It seldom if ever occurs in sound 
parts, but attacks cankered or injured portions, selecting in these places the area 
that lies between the absolutely dead and the perfectly living bark. 
Culiciformis is common here. The larva lives in the stumps of birch trees 
in woods the year after they have been cut down, feeding both under the bark and 
in the solid wood. It is also occasionally found in alder. Insects are capital 
judges of the natural relationship of plants. In the case of these two trees almost 
every larva that I know of that feeds on the one will also eat the other. 
Formiciformis.—The larva of this species lives in osiers, and in company 
with those of the musk and other beetles does a great deal of injury. The books 
say it lives in the shoots ; this is wrong, it is in the buts the larva feeds. 
Icheumoniformis.—This is a good species. It occurs on one or two unculti- 
vated sunny banks in this neighbourhood, Its life-history has only lately been 
