^ 



i88 INJURIOUS AND USEFUL INSECTS 



flies, gall-flies). Mouth-parts of adult adapted for biting, or 

 for biting and sucking. There are usually two pairs of un- 

 equal, membranous, rather few-veined wings, which are some- 

 times wanting. The female 

 is provided with saws, a 

 u^^ sting, or an ovipositor. 



Mn OETHOPTERA 



Structural peculiarities. 



— Orthoptera are never 

 very minute, and some 

 Fig. 98.— Diagram of mouth-parts of bee. of them are among the 



largest of insects. The 

 organisation generally conforms pretty closely to that of the 

 cockroach (Lessons 2, 3, 4, and 36). The wings form 

 externally, instead of being telescoped into the body; they 

 often increase by slow degrees, the new wings being crumpled 

 up within the preceding ones, and liberated at the next moult. 

 They are often useless for flight, sometimes wanting altogether ; 

 in other cases only the fore or only the hind pair are de- 

 veloped, or wings appear in one sex only. In the Saltatoria 

 (leaping Orthoptera), the wings may be largely subservient to 

 sound-production, the chirping organ being variously con- 

 structed in the different families. In Acridiidse the inner 

 face of the hind thigh is rubbed against the roughened outer 

 face of the fore wing. In Locustidse the bases of the fore 

 wings are rubbed together; the inner surface of the left 

 wing bears a file, and the outer surface of the right wing a 

 prominent edge, whose vibration sets up a musical note; a 

 transparent area adjacent to the vibrating edge appears to act 

 as a resonator, and to enforce the sound. Both of the fore 

 wings bear files in Gryllidae. The musical organs are possessed 

 only by the male insects, though the females may be provided 

 with non-functional vestiges. Auditory organs are very fre- 

 quent in both sexes ; they occur on the fore tibia (Locustidse 

 and Gryllidse) or on the dorsal surface of the first abdominal 

 segment (Acridiidse). Leaping Orthoptera are distinguished 

 by the great length and muscular enlargement of the hind 

 thighs. The adult female, and often the immature female 

 also, has generally an evident ovipositor, but this may be 



