AFTER A. 



437 



CATTLE BOT-FLY. Hypoderma, or (Eitrus ftofe. a, Fly. b. Larva, c, Pnpa. b and c, 

 As seen from the under side. (All magnified ; line at left-hand side natural size of Fly.) 



would be unable to move a limb. Another characteristic, however, is required. They must 

 be always kept sufficiently open for the free passage of air, and it is not easy to see how these 

 qualities should be united, as a 

 flexible tube will mostly, if abruptly 

 bent, as is continually the case with 

 the air- tubes of the limbs, lose its 

 roundness at the angle, and shut 

 off the communication. An India- 

 rubber gas-tube is a familiar in- 

 stance of this property of flexible 

 tubes. 



The difficulty is, however, sur- 

 mounted by a simple and yet most 

 effectual plan. The tubes are double, 

 one within another, and in. the in- 

 terspace a line but very strong hair- 

 like thread is closely wound in a 



spiral. It will be seen that, by means of this structure, the tube can be bent in any direction 

 without losing its roundness. The long flexible tubes of Turkish pipes are made in a similar 

 manner, a spiral wire forming the basis, upon which is sewn the leather and silken outer 



tube one of the many instances where the 



ft D t 



art of man has been anticipated in the 

 animal creation. A third species (CEstrus 

 oms), of which we give also an *;xact illus- 

 tration, is parasitic in the sheep, inhabiting 

 the frontal sinus, /. e., the open space be- 

 tween the bones on the forehead a ad between 

 the eyes. 



The Hippoboscidse, 

 popularly known under 

 the name of Forest-flies, 

 deserve a short notice. 

 These are round-bodied 

 insects with legs that can 

 cling with wonderful 



force, and are capable of moving backwards, forwards, and sideways with 

 equal swiftness, so that they are not easily captured, even when they do HORSE, OR FOREST-FLY. 



not take to wing. These insects are mostly found in or near forests, and Hippotosea eyutna. (Mag- 

 nified.) 

 are very annoying to horses and cattle. As may be seen by reference to the 



engraving, their integuments are covered with hair, and are remarkably tough and leathery. 

 The varkms species of Ticks belong to this family, and are closely allied to the Forest-fly. 



Although not included in Mr. Westwood's list of insects, the Lice are mostly considered 

 as belonging to this class, under the name of APTERA. There are very many species of these 

 obnoxious creatures infesting different animals and tribes, and at least three species are found 

 upon the human subject. 



SHEEP BOT-FLY. (Estru* mis. a, Fly. b, Larva. c, Pupa, as seen 

 from the under side. (Everything magnified.) 



