72 



THE AMERICAN ENTOMOLOGIST. 



ious insects I understand those which an- 

 noy man or the useful animals, those which 

 cause real injury to industrial or alimentary 

 plants, and, in a word, to all vegetables, 

 large and small, which are of service to 

 man or animals ; those which, endowed 

 with that marvellous but dangerous in- 

 stinct which enables them to discern the 

 morbid condition of shrul)sand trees, help 

 to hasten their ruin and often render it in- 

 evitable. But I do not place in this cate- 

 gory the greater part of those which attack 

 vegetables only when they are decisively 

 dead, or those which content themselves 

 with the destruction of a few leaves of the 

 vine, the Hazel, the Currant, the Poplar, 

 the Elm, the Oak, etc., and leave only in- 

 appreciable traces of their existence. In 

 short, I include only those which there is 

 some serious reason to fear. Let my ex- 

 clusions be limited to any desired extent 

 under the pretext that a species indifferent 

 because comparatively rare may become 

 common enough to be injurious, and, not- 

 withstanding this concession, I shall es- 

 tablish the following calculation, — which 

 can evidently be only approximate. 



There exist in Europe about 14,000 

 known species of Coleoptera, 500 species 

 of prthoptera, 1,000 species of Neuroptera, 

 5,000 species of Hymenoptera, 2,000 species 

 of Hemniptera, 6,000 species of Diptera, 

 4,000 species of Lepidoptera, and 2,000 

 species of Aptera. This makes a total of 

 34,500 species. Of this number there are 

 at the farthest 350 species truly noxious or 

 capable of becoming so. The others are 

 without interest, from the point of view 

 which we occupy, or, perhaps, useful, be- 

 cause charged with the destruction of our 

 enemies, or designed to restrain the multi- 

 plication of parasitic plants. So that, tak- 

 ing into account the number of the species, 

 we see that, of 100 insects taken by birds, 

 an average of one may be injurious ; of 

 the 99 others the greater part signify very 

 little to us, and a certain nuniber have a 

 mission of usefulness. All this seems sin- 

 gularly to diminish the beneficent role of 

 birds. But, it will be said, it is not exactly 

 upon the number of species that the calcu- 



lation should be based, but upon the num- 

 ber of individuals, for it may be that nox- 

 ious species are much more numerous in 

 individuals than others, — the vine-grub 

 and the grasshopper, for example, — and 

 this would modify the above valuations. 



This objection is very natural, and al- 

 though it is,founded only on a hypothesis 

 which it would be impossible to support 

 by figures, as it would be not less impossi- 

 ble to answer it by figures, we will ap- 

 proach it in another manner, and discuss 

 not in general terms, but relatively to the 

 most noxious species taken separately, the 

 role which birds may play. 



[To be coiitiuucd.^ 



REMARKS ON A NEW FORM OP JASSID. 



The North American Continent is ten- 

 anted by a group of small Homoptera be- 

 longing to the family Jassida, which prom- 

 ise to yield very destructive species to the 

 future agriculturist. They may be found 

 upon the low bushes, or swept from grassy 

 plants which grow in fields and meadows 

 along the edges of thin woods. I add 

 here the description of one of them to 

 which my attention has been recently 

 directed: 



^ CicADULA EXITIOSA N.Sp. Long sub-fiisiform, 

 ground-color pale testaceous, polished above, 

 but dull beneath ; the upper surface of the abdo- 

 men black, excepting the lateral and hind 

 margins of the segments. Face yellow, crossed 

 each side by a series of slender, brown, curved 

 lines, the outer cheeks with two brown long spots, 

 and the forehead with a roundish, black spot each 

 side of middle, exterior to which the reddish 

 brown ocelli are seen next the suture, and below 

 the latter is a small brown spot of about their 

 size; in the middle is usually a small, brown dot. 

 The vertex is arcuated; with the tip a little angu- 

 lar, the surface on the posterior half transversely 

 depressed, and marked with a curved, brown, 

 transverse cloud, which has two blackish dots 

 just behind it, a small spot near each outer angle 

 and a slender streak along die middle ; any one, 

 or several, of these are sometimes absent. Pro- 

 notum with a whitish line in the middle and a 

 short oblique one each side, anteriorlj^ is a strongly 

 curved series of longish brown dots, and on the 

 posterior half, occasionally a few obscure', cloudy 

 marks. Scutellum with a pale line on the mid- 

 dle running through a brown spot, or only a faint 

 cloud instead ; each side, basally, with a whitish 

 oblique line, and near each basal angle is a del- 

 toid brown mark, or line. Hemelytra translu- 

 cent, or faintly tinged with brown, narrow, mod- 

 erately valvate, the costal nervule pale, moderately 



