SPIDER-LIKE ANIMALS 



393 



aquatica), which constructs a thimble - shaped nest under water, 

 attaching it to surrounding objects by mooring-strands which also 

 serve to snare prey. The nest is filled with air, which the spider 

 brings down in the form of bubbles adhering to its hairy abdomen. 

 Examples of common British spiders which do not construct 

 webs are the Wolf- Spiders (Lycosida)> and the handsomely- 

 striped Harlequin- Spider (Salticus scenicus), distinguished by its 

 leaping powers. 



Order 7. MlTES (Acarina) 



Mites, as their name indicates, are minute forms, and they 

 embrace an exceedingly large number of species, some of which 

 are found almost everywhere. A typical example is the Cheese- 

 Mite ( Tyroglyph^ls siro) (fig. 240). The abdomen 

 is unsegmented and closely fused with the 

 cephalo-thorax, the entire body being oval in 

 shape. The small chelicerae are provided with 

 pincers, and the pedipalps are short and slender. 

 The usual four pairs of walking- 

 legs are present, two directed for- 

 wards and two backwards. Re- 

 spiratory organs are absent. An- 

 other well-known species is the 

 " Red-Spider " or " Money-Spin- 

 ner", which lives on the juices of leaves and spins a 

 protective web. One of the chief features in which 

 it differs from the Cheese- Mite is in the possession 

 of breathing organs, which are in the form of air- 

 tubes. Other examples of the group are Ticks, 

 Mange- Mites, and similar pests, which will be dealt 

 with in another section. 



UTfl 



Fig. 240. Cheese - Mite 

 (Tyroglyphussiro},szz.n from 

 below. Enlarged forty times. 



Order 8. TONGUE- WORMS (Linguatulidae) 



Fig. 241. Tongue- 

 Worm (Pentastotnum 

 tcenioides} 



Tongue -Worms are worm -like forms which in 

 the adult condition are found as parasites in the nasal cavities 

 of Dog and Wolf. The only appendages are two pairs of hook- 

 like structures in the neighbourhood of the mouth. Pentastomum 

 tcenioides is the type (fig. 241). 



