INSEC? LIFE IN INDIA AND HOW TO STUDY IT. 175 



7. Diptera ( s/$ double, *n/n» a wing — two-winged). Two mem- 

 branous wings. Mouth suctorial, but varying greatly. Metamorphosis 

 complete. (Two-winged flies such as house fly, mosquito, &c.) 



8. Thysanoptera ( 9 vaxvot fringe, <* T tpi» a wing — fringe-winged). 

 Four very narrow fringed wings. Mouth imperfectly suctorial. Me- 

 tamorphosis incomplete. 



9. Hemiptera (^< half, wipo* a wing — half-winged). Four 

 wings : the front pair either leather-like, with the upper portion 

 more membranous, or entirely parchment-like or membranous. 

 Mouth perfectly suctorial. Metamorphosis incomplete. (Includes 

 tree bugs, cicadas, plant lice, scale insects.) 



It must be remembered that numerous exceptions exist to these cha- 

 racters in most of the great Orders : for instance, wingless forms are 

 by no means rare in several of the Orders. 



Chapter III. 

 Order I. Aptera. 

 Small insects with a weak outer skin, destitute throughout life of wings, 

 but with throe pairs of legs ; antennae large or moderate in size. These are 

 tho most primitive forms of insects. The Order is mentioned here as. it 

 includes the Sub-Order Thysanura to which the common so-called fish- 

 insect of India, a species of Lepisma (Family Lepismatidae), belongs. Fig. 5 

 shows the common Calcutta insect. Most of the Thysanura are small, 

 soft-bodied, with feebly developed mouth parts, and live in damp earth 

 among decaying vegetable matter. Some live under the bark of dried and 

 decaying trees or in decaying wood, and 

 in rare instances species are found pre- 

 ferring dry and warm localities. Amongst 

 the latter is the above-alluded to fish- 

 insect. It is well known to all in India, 

 and perhaps does most damage in libraries 

 and to pictures. In the latter it apparently 

 feeds upon the saccharine material used in 

 mounting the picture in its frame. Such 

 should either always be mixed with 

 arsenic, or naphthaline powder should 

 be dusted over the picture back. Book FlG . 6 _ A FwMnsect. Zepiima 

 eases should be freely powdered with naph- sp. (Calcutta.) 



thaline to preserve the books. In the record-rooms of kutckerries, &c, 



