Invertebrate Gallery of the Indian Museum. 91 



compare some of the more obvious external structural 

 characters of Insects, and to illustrate the natural classifi- 

 cation of this Class of Arthropoda, as well as to exhibit 

 some stages in the life-history of certain insects that affect 

 agricultural industries. 



i. HEXAPODA THYSANURA. 

 [(Ease 70^]. 

 The familiar '^ fish insect", which eats books and clothes, 

 illustrates this small Order. The Thysanura are wingless 

 insects with hairy or scaly integument and rudimentary 

 mouth-parts. They have a general external resemblance 

 to centipedes. They do not pass through a metamorphosis. 

 By some zoologists they are regarded as aberrant Orthop- 

 tera. 



• ii. HEXAPODA ORTHOPTERA. 

 [OCases ZOf-ZSOT]. 



Insects with typical biting and masticating jaws, and 

 with two pairs of wings, the front pair of which are often 

 parchment-like. In the females of some species, however, 

 the wings are absent or rudimentary, as may be seen in 

 some of the exhibits of Mantidas. The abdomen usually 

 ends in rods or stylets, which in the female (as in the 

 locusts) may be used as ovipositors. 



In many Orthoptera {e.g., the Crickets, Locusts, and 

 Grasshoppers) the males produce powerful musical sounds 

 by the rhythmical scraping together of file-like plates 

 which are developed either at the bases of the hard fore- 

 wings or on the inside of the "thighs" of the last pair of 

 legs : in the first case the wings of opposite sides are 

 scraped across one another, one wing serving as a bow 

 and the other as a fiddle ; and in the second case the thigh 

 is used as a bow, being scraped against the fore-wing which 

 acts as a fiddle. It is only very exceptionally that these 

 sound-producing or stridulating organs are possessed by 

 the female also. 



