The Zoologist — March, 1869. 1585 



so many widely different species, are identical — to sketch or describe 

 them would be mere repetition. The head is triangular, broad at the 

 base, with the apex somewhat prolonged, forming a sucking mouth ; 

 there are six short legs, three-jointed, and armed with acute single 

 claws : these claws are moveable and close between two small projec- 

 tions, thus forming a very efficient forceps: they cling by this means 

 to the barbules of the feather with great tenacity, and are extremely 

 difficult to detach. Compared with the true parasite they are a slow, 

 sluggish moving insect, and, placed on a smooth slide of glass, as help- 

 less as the famed Italian knights who, overthown, lay immovable in 

 their heavy armour, like lobsters. The true distinctive parasite is a 

 very nimble fellow, running rapidly, even over a smooth surface : their 

 feet seem to be used in quite a different manner to the "tick's" — in 

 the one case formed for grasping, in the other for progression. The 

 abdomen in the " tick," at its juncture with the short thorax, is as wide 

 as the base of the head, but gradually increases in width for two-thirds 

 of its length, and then rapidly contracts. The sides of the abdomen 

 from thorax to extremity are encased with horny plates, overlapping at 

 the angles of the body, but disconnected towards the centre : these 

 plates are pierced along the lower edge with minute round holes for 

 half their length : in the remainder of the plates, towards the centre of 

 the creature's back, which is uncover ,d, the edges are only scalloped : 

 it is difficult, however, to give a clear idea without drawings. The body 

 and six legs are thinly covered with long hairs ; there are two many- 

 jointed feelers placed one on each side of the head, and just above 

 them respectively a smaller process, the use of which I cannot deter- 

 mine. These creatures are remarkably tenacious of life : I have found 

 them, after having been gummed to paper and passed through the post, 

 quite lively. But the most remarkable instance of vitality was shown 

 in one taken from a hooded crow : one evening I fastened this insect 

 with a little gum to a glass slide, purposely leaving its head and 

 thorax free, the better to see the construction of its legs: six days 

 afterwards, on placing the slide under the microscope, I was as- ■ 

 tonished to find it as active as ever, and struggling to free itself from 

 the gum. These "ticks" are uniforndy of a bright brown or burnt- 

 sienna colour. 



With the exception of these " ticks," which appear common to all 

 alike, I believe it will be foutid that every species of bird has its own 

 distinct and characteristic insect. A batch of parasites taken from a 

 bird and placed on the same slide, side by side, and examined 



SECOND SERIES — VOL. lY. O 



