THE AC ARID A. 



445 



feeling here and there. The larva perforates the pear leaves from 

 beneath, and lives under them, forming gall-like excrescences, but 

 which are not true galls ; it has only four legs. After its meta- 

 morphosis a perfect insect with eight legs comes forth. 



The Itch Insect, of which a representation is given, is one of 

 the Acarida or spiders with unsegmented bodies and palpi, which 

 enable them to adhere. It undergoes metamorphoses, and the 

 larva has six legs. The female burrows under the skin, and the 

 male lives upon the surface of the human body. 



M. Robin states that the mites pass through a series of meta- 

 morphoses ; a six-legged larva issuing from the t^^ becoming 



ITCH INSECT. 



converted into a nymph, from which the adult mite proceeds. He 

 has observed in the mites which attack birds in cages {Sarcoptidcz) 

 a more complicated series of phenomena. In them the males pass 

 through four and the females five stages. The &gg in issuing from 

 the animal has the form of a hexapod larva (six-legged) and is 

 followed by a stage of a nymph with eight legs, but without any 

 organs of reproduction. These turn into sexual males, which moult 

 once, and become perfect, or into females. These are like the 

 nymphs, and moult, and produce the perfect female which lays eggs. 

 The ticks which stick to so many animals and suck their blood 

 are spiders, but in their early life they have some of the charac- 

 teristics of true insects. Thus, the moose tick collects upon those 

 fine deer when they arc in the forests, and irritate them greatly. 

 The eggs of this tick, when they are hatched, open like the valves 

 of a clam shell, and a six-legged creature comes forth from each. 



