360 



UTILITARIAN ZOOLOGY 



Injurious Spider- like Animals (Arachnida). — The only 

 forms of great importance here are the Mites [Aca^'ina). Mange- 

 and Itch-Mites, injurious to domesticated animals, have already 

 been mentioned (see p. 196). Poultry are attacked as well as 

 quadrupeds. Fowls are also liable to be infested by Red Fowl- 

 Mites (Dermanyssiis gallvKZ), which suck their blood and set up 

 an intolerable itching. 



Domesticated animals are also often attacked by Ticks 

 {Ixodidce), which are able to draw large quantities of blood, and, 

 what is more serious, may convey the germs of disease. Infec- 

 tion by means of one such 

 Tick {Ixodes reduvins) is, 

 for example, the cause of 

 " louping ill" in sheep. 



Cultivated plants also 

 suffer from the attacks of 

 Mites, among which the 

 following may be men- 

 tioned : — Currant Gall - 

 Mite [Pliytoptus ribis). 

 Red Hop-" Spider" {Te- 

 tranychiis telarius\ Red 

 Plum- " Spider " (7". ru- 

 bescens), and Harvest or 

 Gooseberry - " Bug " ( T. 

 mitiunnalis). 



Other kinds of Mite 

 spoil furniture and attack 

 food, especially meal, 

 cheese, and sugar. 



Injurious Myriapods 

 (Myriapoda). — Some of the Millipedes ("false wire-worms") 

 attack the underground parts of various plants, or may damage 

 soft fruits. 



Injurious Flat-Worms (Platyhelmia). — A large number of 

 Flukes (Trematoda) and Tape-Worms (Cestoda) are parasitic 

 within the bodies of domestic animals, as previously stated in 

 dealing with the personal enemies of man (see p. 342). A few 

 details may be appropriately added. 



Fhikcs {Trematoda). — It is only necessary here to refer to the 



Fig. 1257. — Stages in Life-History of Liver-Fluke [Fasciola 

 hcpatica], enlarged, a, ciliated larva: b, sporocyst, within which 

 redia; are developing: c, redia, within which a new generation of 

 redias is developing: d, redia, with contained cercarise (G, opening 

 by which these escape: Z>, intestine): E, cercaria. 13 to E are 

 parasitic within the water-snail f [Lintmea trwicatula)^ from which 

 E escapes to encyst on the stem of a plant. 



