with Descriptions of several Hymenoptera. 119 



cies : Dejean, in his Catalogue, enumerates 1073 ; and Schon- 

 herr, who has devoted very great attention to this group, will 

 shortly publish the description of the species, which will 

 occupy three or four octavo volumes. I understand, the first 

 volume of this work is now in the press, and that it will be 

 published in Paris, under the superintendence of M. Boisduval. 

 Mr. Stephens has described more than 500 British species.* 



In the genus ikfusca of Linnaeus, which comprises several 

 very distinct modern families of two-winged flies, that author 

 described 129 species. Of these modern families, I shall only 

 refer to that of the ilfuscidae, of which the house-fly is the 

 type. Of this family, Meigen has described nearly 1700 

 European species, and about the same number (belonging, 

 however, only to a portion of this family) have been described 

 by Robineau Desvoidy, in his Essai sur les Myodaires, a quarto 

 volume of 812 pages, many of which are extra-European. 

 In England, there have been recorded about 700 species. 



The only remaining Linnaean genus which I shall notice is 

 the magazine-like one of ichneumon, comprising (like Musca) 

 several modern families, all of which are parasitic upon other 

 insects. In this genus, Linnaeus described 77 species. Gra- 

 venhorst, in his Ichneumonologia Eurvpcsa (containing nearly 

 3000 octavo pages), describes nearly 1650 European species 

 of genuine Tchneumonidae ; the majority of which will, 



* With respect to the relative proportion of the different orders to each 

 other, Messrs. Kirby and Spenee state that the Coleoptera may be consi- 

 dered as forming at least 1 to 2 of our entire insect population. Now, how- 

 ever, that the same attention is bestowed upon the minuter Hymenoptera, 

 Diptera, and Lepidoptera, as has been long given to the small Coleoptera, 

 we find this calculation gives too great a share to the beetles. In Mr. 

 Stephens's Catalogue, they barely reach one third of our native insects. If, 

 therefore, we take the group of predaceous beetles (being the one which 

 has been most recently investigated in the detail of its species with all pos- 

 sible advantages and assiduity by Dejean), we find that, although it did 

 not bear, in the Systema Naturce, a greater proportion to the whole order 

 of beetles than 1 to 16, yet not only in Stephens's Catalogue of the English 

 species, but also in the general Catalogue of Dejean, the proportion which 

 it bears to the whole Coleoptera is about 1 to 16. And, as I have already 

 stated that the number of species described by Dejean may be averaged at 

 2000, the whole number of beetles, at the above rate, would not exceed 

 16,000; and, by adding 4000 more for other known species, the number 

 would not exceed 20,000: and yet Count Mannerheim, in his recent 

 monograph upon the 5taphylinidae, states that Dejean had informed 

 him in 1830 that he then possessed nearly 18,000 Coleoptera; and the 

 baron himself informed me, two years ago, that he possessed between 

 20,000 and 21,000 Coleoptera. And by estimating the beetles, as above, 

 at 1 to 3 of the insect tribes, we shall only obtain 60,000. What a wide 

 field, therefore, remains to be investigated, before we shall become acquainted 

 with the 600,000 or even 400,000 species supposed by Messrs. Kirby and 

 Spenee to exist ; and how absurd does it seem to consider our systems, or 

 rather system, as firmly established, whilst so little is comparatively known ! 



i 4 " 



