young and fully grown larvæ ; c, pupa; d, beetle; e, left wing cover, magnified; f, leg, magnified) has chiefly attracted attention at the West during the few years past. It has been very destructive, hence anything bearing upon its habits is

interesting to farmers. Last year they were more numerous in Illinois than at any other time. Whole acres were entirely destroyed by them. The autumn following the early frosts that killed the potato vines, was one of the finest we ever enjoyed. This unusually late pleasant weather induced the pup of the last brood of the Colorado Beetle to mature and come out of the ground instead of remaining in over winter, and the lack of food in the fall, together with the cold open winter, contributed greatly to their destruction. From this one can easily see their assailable points, and devise means for holding them in check. It is manifest that this can be done most effectually by the concerted action of the farmers of the whole country. I think it needs no argument to prove that it would be better for the entire North-west, so far as the Colorado Beetle has extended, to abstain from planting potatoes for one year, than to be annoyed as they have been. in Iowa and Illinois during the few past years. Or, perhaps, it might be as effectually managed by planting only early

maturing varieties; planting these early one year, and digging the potatoes in August; then in the following year farmers might plant about the first of July, and take them up after the frost kills the vines. By this course of treatment these potato bugs will be without food during the first fall, and many will perish, while those that remain in the ground over winter will come up in May, and be without food more than a month in the spring, and thus perish. This plan rigidly followed will restrain, if not exterminate the bug.

To this argument some may reply that the potato bug will feed on other species of the natural botanical family Solanaceæ, such as the tomato, thorn-apple, etc. It is true that they will eat of these to some extent, especially the hungry halfgrown larvæ, but I have observed carefully, and never in this region saw the young potato bugs developing from the eggs laid on these plants, though I have occasionally seen eggs on tomato plants.

Early in the last spring a sufficient number of mature potato bugs appeared on the potato vines to cause some apprehensions of trouble, though much less than in the preceding year. The larvæ appeared as usual, and early potatoes were partially trimmed by them, from which I inferred that the second brood would do a good deal of damage in July and August.

About the middle of July I saw potato bugs in Minnesota, as far north as St. Paul. They were quite abundant, the larvæ stripping the vines as they had done in Illinois last year. I was at home in Illinois in August, and sought for the potato bugs on the same grounds that were entirely overrun by them last year, and found very few. At the last of August, I searched in the potato patch, on these same grounds, and found but two mature bugs and one small bunch of eggs. Here is a remarkable and unexpected decrease of bugs, instead of the usual increase, that makes them very destructive in August. How are we to account for it? The various known heteropterous enemies, and Lady-birds,

(Fig. 14, Coccinella 9-notata and pupa; fig. 15, Hippodamia 13-punctata; a, larva; b, pupa) without doubt destroyed some, but as I could not find them more numerous than usual,

Fig. 14.

I cannot admit that they were the chief means
of this almost perfect extermination of potato
bugs. Moreover the larvæ in June were suffi-
ciently numerous, in propor-

tion to the number of beetles
observed in the spring, and

Fig. 15.

b

yet in July and August the beetles failed to appear as expected. We can only look to climatic causes as the principal means that prevented the spring brood from maturing.

a

The weather here was uncommonly hot as well as dry, hence the pupa were exposed to the burning dry dust, and this doubtless was the efficient cause of the death of the soft, naked, delicate pupa. The only object that they can have in entering the ground to transform, is protection from the hot dry atmosphere of summer and the cold frosts of winter, for they will transform well enough above ground in a pasteboard box in a room, as I proved in hundreds of examples during the series of observations I made on the breeding of these insects in 1865, and reported in the "Practical Entomologist." The ground usually furnishes a cool moist place, but this time it failed to favor them, hence they perished.

I have often observed that the pupa of various insects perish from exposure to too much evaporation. The pupa of the various wood-borers however, carefully handled, will not develop so well in a paper box as in the hole they make in the tree, and many of them dry away entirely; this I have often observed, and very forcibly this summer, in the examples of the new species of beetle, that I have bred from the prickly ash tree; also the three varieties of beetles, bred from the several borers, or "grubs," found in the grape-vine, reported to the Academy of Natural Sciences, Philadelphia. This same drying away of the pupa I have often noticed

in attempting to breed the Maple Worm (Dryocampa rubicunda). The larva retires to some cool moist place beneath a board, stone, or anything it can find on the ground, where it will not be exposed to the dry atmosphere, for the chrysalis is naked. Now take this same chrysalis and put it into a dry box, and it most likely will perish, and fail to perfectly develop. Many lepidopterous larvæ protect themselves with an impervious cocoon where they are exposed to atmospheric vicissitudes. This, I believe, is not only to protect them from the rain, if it is at all for this purpose, as entomologists often suppose, but to protect them from the far more injurious influence of evaporation during the long time they take no liquid nourishment. It is for this purpose also that the Cecidomyian larva cements its spun cocoon with a gummy fluid, as I have shown in the "Transactions of the American Entomological Society," for October, 1867. We therefore find here another example of climatic causes, producing disease and death among insects in a wholesale man

ner.

Entomological writers usually represent cannibal insects as the most efficient means in nature for the extermination of injurious insects, and in the reports of State Entomologists we occasionally find them speaking in glowing terms of the power that man can exert in controlling injurious insects. While we may not despise these measures of protection, especially the former-for without the Ichneumon fly, the Syrphus fly, the Coccinella, etc., we would doubtless be overrun by swarms of caterpillars, plant-lice, and other noxious depredators-let us not forget the great truth, that climatic causes, producing death by epidemic diseases and various other means, are infinitely in advance of most other natural means of exterminating noxious insects (for my extended. views and observations on this topic, see an address before the Northern Illinois Horticultural Society, and published in the first volume of the Transactions of that body, and my Report of a remarkable epidemic disease observed among

Chinch-bugs, in the Proceedings of the Academy of Natural Sciences of Philadelphia, for May, 1867).

Fig. 16.

In the case of the Chinch-bug, the conditions favoring its development and health are entirely the reverse. It was during the unusually wet weather of 1865 that the great epidemic referred to prevailed, and at the same time the Fig. 17. Colorado potato bug flourished and mul

tiplied as favorably as it could desire; but this year was one favorable to the development of the Chinch-bugs, and true to nature, they have increased so that a few can be found again. Since I observed this failure of development among the potato bugs, I have looked carefully for them in this (Carroll) and parts of the adjoining counties, and seldom find a patch with any bugs. At this date the early frosts have

a

Fig. 18.

already killed the

potato vines, hence their autumnal supply of food being cut off we may expect a still more complete destruction of the bugs if

the next autumn should be nearly as pleasant as the last. Of the Blistering Beetles (Cantharide), I have observed this year the Striped Cantharis (Lytta vittata Fabr., Fig 16) unusually abundant, and quite injurious to potato vines, beet leaves, etc. The Margined Cantharis (Cantharis marginata Oliver, Fig. 17) were also moderately abundant, injuring beets most. I also observed some of the Ash-colored Cantharis (Lytta cinerea Fabr., Fig. 18, a, male), and the black Cantharis (Lytta murina Leconte, Fig. 18, b) on potatoes and beets. A species of Oil Beetle (Meloë angusticollis, Fig. 19) was also abundant, eating potatoes, beets, etc., and injuring tomato fruit very much. Farmers all about