PREFACE. XVII 



sure to belong to different species. A few instances will suffice 

 to illustrate the quality of the work of this author. Of the two 

 North American Enmcrns, described by Walker, the one proves, 

 upon examination, to be a Hdopliilus, the other, the common 

 Mcsograpta gcmhiata. A North American Plecia, described in 

 the Diptera Saundersiana , puzzled me for a long time, until I 

 saw the specimen , which proved to be a common female 

 Dfloplws, with a red thorax. Mr. Walker's Tliercva plagiata 

 is the well-known S+.icliopogon trifasciatus ; his Asyndidiim tenuipcs 

 is Blerpharoc&ra capitata Loew ; and the common Cordylura bi- 

 macidata is described as Lissa varipes. When such blunders 

 are committed with as striking and easily recognizable forms, as 

 Dilophus or Blepharocera, what can be expected from Mr. Walker 

 in the discrimination of species in such genera as Culex, Bibio, 

 Clirysops, Tabanus, Anthomyia and the smaller acalypterous 

 Muscidae ! These doings were not confined to the North American 

 portion of the collections, which Mr. Walker had under his 

 care. To quote a single instance, the Musca Aluta n. sp. List 

 etc. IV, p. 911 ; (the pain a is given as ,,LaplandV", ,,France?"), 

 is represented in the British Museum by seven specimens, which 

 are nothing but our old friend Stomoxys calcitrans; an eighth 

 specimen is an Anthomyia. The passage at the end of the de- 

 scription: ,,In one wing of an insect of this species, the lower 

 cross-vein sends forth a stump into the disc" , refers to this 

 latter specimen , and this passage proves that Mr. Walker 

 looked with some attention at it, without perceiving that it 

 belonged to a different, and very easily distinguishable genus, 

 and even to a different family ! 



' Mr. Walker's identifications of the species of former authors 

 are often, I may say in most cases, incorrect. Thus, when 

 in his description of Tabanus imitans Walker, he compares it 

 to T. abdominalis, Fabr., he means T. fuscopunctatus , Macq. 

 which he took for abdominalis. 



These facts are given as a warning for entomologists not 

 to trouble themselves too much about the interpretation of Mr. 

 Walker's descriptions , because in most cases, they will find 

 themselves misled by the very data furnished by him. And it 



