38o 



CHARACTERS OF INVERTEBRATE ANIMALS 



fowl is infested by no less than five species [Menopon pallidum 

 and others), and the " dust baths " in which this bird indulges 

 are no doubt taken with a view of getting rid of these and other 

 parasites. Mammals are less troubled with attacks of the kind, 

 the dog being an example of animals which are thus attended. 

 Trichodectes latus is the name of its unwelcome guest. 



Order 8. — Straight-winged Insects (Orthoptera) 



The Cockroach, of which an account has already been given, 

 may be taken as a type of this order, which also includes such 

 familiar forms as locusts, grasshoppers, earwigs, and crickets. 

 The mouth-parts are adapted for biting, and it is particularly to 

 be noticed that the second maxillae are not so closely fused 

 together to form a lower lip or labium as in most other insects. 

 The fore-wings are modified into leathery wing-covers, and the 

 large membranous hind ones are usually traversed by nervures 

 radiating from the point of attachment, and are thus enabled to 

 fold up in a fan-like manner when not in use. There can 

 scarcely be said to be a metamorphosis, for the young insects 

 when just hatched differ from the adult mainly in size and in 

 the absence of wings, while there is no quiescent pupa stage. 

 It is supposed that at least 10,000 species of recent Orthoptera 

 exist, including the largest known insects, but of this large 

 number less than forty are native to Britain. A distinction is 

 drawn between: i. Running Orthoptera, including Earwigs, Cock- 

 roaches, Soothsayers, Stick- 

 Insects, and Leaf- Insects; 

 2. Leaping Orthoptera, em- 

 bracing Grasshoppers, Lo- 

 custs, and Crickets. 



I. In Running Orthoptera 

 all three pairs of legs are 

 pretty much alike. The 

 Common Earwig {^Forficula 

 auricularia) (fig. 230) may be 

 taken as a type of a family 

 in which the wings are folded up in a remarkably complex manner 

 under the short wing-covers, and the tail is provided with curved 

 forceps. No satisfactory explanation has been given of the curious 



Fig. 230. — Common Earwig [Forficuta auricularia) 

 Adult (line indicates actual size) and earlier stages 



