o ^ 
OO 
destructor), and the wheat midge (Cecidomyia tritici). The others would mostly 
fall into the third and fourth classes, though a few, which are sometimes 
quite injurious to corn and wheat in the granary, might, perhaps, be 
properly regarded as having a second-class importance. 
“General feeders are, first, the white grub: second, the destructive grass¬ 
hopper of the western plains; third, the army worm: fourth, the stalk- 
borer; and fifth, the cutworm, under which general or generic term I 
include a number of closely allied species, all of which are the caterpil¬ 
lars of a family of moths known as the Agrotidav None of these general 
feeders, however, are sufficiently destructive, nor so generally diffused as to 
rank as first class noxious insects; but they may all be properly admitted 
into the second class. 
“Of the insects injurious to domestic animals, we admit but three into 
the selected list of one hundred species, and these are the bot flies, re¬ 
spectively, of the horse, the ox, and the sheep. The bot fly of the sheep 
may, perhaps, be admitted into the second class, but those of the horse 
and ox can not rank above the third class. Indeed, it is an unsettled 
question whether the bot fly of the horse is ever seriously injurious to 
that animal; but it may very properly be admited into the list on account 
of its very curious history, and the uncertainty which still attaches to its 
real influence upon the horse.*’ 
Principal agencies opposed to the spread of insects are climatic influ¬ 
ences, insectivorous birds and animals, parasitic insects, and human instru¬ 
mentality. Insects reviewed at length with reference to these sources of 
opposition are the codling moth, plum and peach curculio, cankerworm, 
oyster-shell bark louse, and Colorado potato beetle. 
The codling moth.—Larva and pupa probably not materially affected by 
meteoric influences; but cold or violent storms at time of egg-laying may 
seriously interfere with this process, and thus cause the well-known varia¬ 
tions in its abundance from year to year. A few pupa?, probably poorlv 
protected, fall a prey to parasitic ichneumons. Its only really efficient 
enemies are the woodpeckers. Great numbers of worms are caught by 
the usual method, that of capturing them under bands, but this fails in 
two respects; they are not captured until after the season’s injury is done, 
and it is not effective if other infested orchards are nearby, without coop¬ 
erative effort, which is difficult to secure. However, its use is strongly 
advised. 
The plum and peach curculio.—If left to himself, he leaves not a single 
plum, and rarely a peach. So far as the plum is concerned we have vir¬ 
tually abandoned the field. As to the peach the conflict is still main¬ 
tained. Perhaps ten dollars per hundred trees is a reasonable estimate of 
the cost of keeping him in check. Natural agencies help but little. Dry 
weather following wet may imprison in the ground the transforming 
larva?, since curculios, previously scarce, sometimes swarm after a warm 
rain; but this can only happen in stiff clayey lands. 
The cankerworm.—Has been steadily on the increase in parts of Northern 
[llinois where it has ruined a number of orchards. When overtaken 
by cold storms of rain or snow they are merely rendered torpid for a time. 
Usually very persistent, but sometimes rapidly disappear. Perhaps due 
to bad weather when larvae are young. Sometimes birds, notably fhe 
3edar bird, eat them largely. 
The oyster-shell bark louse.—This has been on the decline for ten years 
jr more, and is almost completely destroyed south of the 42d parallel- 
the work of its insect enemies. 
The Colorado potato beetle.—The only seriously destructive insect which 
uis come from the west. When unresisted it takes the whole crop. 
Natural enemies have not appreciably checked it, except in a few locali¬ 
ses. Its destruction by hand picking, machinery, and Paris green lias 
>een of the most wholesale character. 
In studying insects, we find that nature always tends to restore her 
ost balances. 
