TYPE TRACHEATA. 



511 



ra = mandibles. 

 mx = maxilliE. 



damage to apple-trees. The remarkable lieterogony of these 

 forms has already been described (p. 498). 



In both the suborders the mouth-parts are adapted for 

 piercing and suckiug. The 

 labium (Fig. 238, B, 11} is 

 prolonged into a slender, 

 usually four-jointed process, 

 grooved upon its upper sur- 

 face, the groove being con- 

 vertible into a tube by the 

 closure over it of the long 



slender mandibles (in) and 



. , -i i c FIG. 238. .4, Anasa tristis; B, MOUTH- 



maxillae (mx} which form long pARTg QF Nepa c .^.^ (aftep SAVIQNY 



slender needlelike piercers, from OWEN). 



The antennas are usually ^ == labium. 



short and filiform, though 



in some of the Heteroptera they may be almost as long as 



the body. 



Many of the Rhynchota are provided with glands which 

 secrete an offensive fluid, e.g. in Cimex and Anasa, and in the 

 Coccidse wax-glands are also abundantly present, producing 

 a secretion which may cover the body with waxen scales, or 

 in some cases form a wool-like mass covering the greater 

 part of the abdomen (Pemphigus). The Aphidae also possess 

 as a rule upon the antepenultimate abdominal segment a pair 

 of tubular elevations or papillae from which a sweet secretion 

 issues, the so-called "Honey-dew," which covers the leaves 

 and stems of the plants upon which the Insects live, and is 

 eagerly sought for by various Insects, more especially by 

 Ants. 



The larvae of the Ehynchota as a rule resemble the adults 

 even to the structure of the mouth-parts, and the metamor- 

 phosis is consequently gradual. The Cicada forms, however, 

 an exception to this rule, the larva occurring beneath the 

 surface of the ground and living upon the roots of trees. 

 It becomes transformed into a pupa, which, however, con- 

 tinues to lead an active existence, becoming quiescent only a 

 short time before the moult which results in the formation of 



