412 CUARACTERS OF THE GENUS TACIIYCINETA 



taxed to supply voracious throats with insects captured on 

 tireless wiug. The rate of speed iu flying, the distances tra- 

 versed in a given period, and tbe numbers of insects destroyed, 

 have all been tbe subjects of some curious calculations, — or 

 rather speculations, for these matters scarcely admit of mathe- 

 njatics. Wilson supposed a Swallow to fly about a mile a 

 minute, for ten hours a day, for ten years, — equivalent to more 

 tban eighty-seven times around tbe world! However this may 

 be, let us trust that these matchless wings may bring the Swal- 

 lows again next year, as they have thisj and let us look leni- 

 ently, even encouragingly, upon the various superstitions of 

 folk-lore, which tend to protect and foster these amiable, these 

 charming and useful creatures — even though we may not fear 

 that to kill them is to make the cows give bloody milk ! 



Genus TACHYCINETA Cab. 



Hirundo, p., of authors. 



Chelidou, Boie, lais, 1826, nee 1822 (originally applied to H. urbiea). 



Tacbycinet.i, Oab. Mus. Hein. i. 1850, 48 (type R. thalassina). 



Tbis group was established in 1850 by Cabanis upon H. 

 thalassina of Swainsou, and is now commonly allowed to 

 include iZ. hicolor. These species agree closely with each other, 

 both in form and pattern of coloration, and differ from Hirundo 

 proper chiefly in lacking the disproportionate lengtb, attenua- 

 tion and forfication of tbe tail, tbis member being much shorter 

 than tbe wings, and simply emarginate or with shallow fork. 

 All the species are entirely white below, and tbe extralimital 

 ones, of wbich there are several, have the rump wbite. The 

 eggs of our species are pure wbite, unmarked. H. thalassina 

 stands alone iu the soft velvety plumage of the upper parts, 

 without metallic gloss, and much variegated iu color. Tbe 

 other species, including T. Mcolor, have more compact, silky 

 plumage, with rich metallic sheen. A difference was noticed 

 by Cabanis, who speaks of T. hicolor ,, als 2te, jedoch vom 

 Typus mebrfach abweicbeude Art." None of tbe many 

 generic names bestowed of late upon Swallows bave been 

 based upon T. hicolor^ which seems at least as worthy as some 

 otbers to stand as type of a subgenus (Iridoprocne). This 

 includes, besides /. hicolor^ tbe extralimital species I. albiven- 

 tris, I meyeni, I. leucorrhoa, I. albilinea, and probably some 

 otbers. Tbe wbole group is confined to America. Both of the 

 North American species occur iu tbe Colorado Basin. 



