STRUCTURE 



537 



rapidity of the current is increased by a pumping action of the 

 pharynx, and possibly by movements of the setae themselves. 

 Though the setae are often extremely elongate — sometimes several 

 times the length of the body — they are nearly always slender, and 

 there is no reason to suppose that a perfect, or air-tight, tube is 

 formed ; hence it is probable that capillary attraction is really 

 the chief agent in the ingestion of the fluid. The slight diversity 

 of structure of the Hemipterous trophi is in very striking con- 

 trast with what we find in mandibulate 'Insects, and in the less 

 purely suctorial Insects, such as Diptera and some divisions of 

 Hymenoptera. Schiodte in com- 

 menting on this has suggested that 

 it is probably due to the small variety 

 of actions the rostrum is put to.-^ 



The head exhibits great variety 

 of form ; in the Homoptera the 

 front part is deflexed and inflexed, 

 so that it is placed on the under 

 surface, and its anterior margin 

 is directed backwards ; it is often 

 peculiarly inflated ; in the Lantern- 

 flies or Fulgoridae (Fig. 282) to an 

 incomprehensible extent. In the great 

 Water-bugs, Belostomidae, there is on 

 the under surface a deep pocket for 

 each antenna, beautifully adapted to 

 the shape of the curiously-formed ap- 

 pendage (Fig. 279). The prothorax is 

 always very distinct, frequently large, 

 and in many of the Heteroptera 



(Fig. 257), as well as in tlie Homop- Fig. 257 .- Saccoderes tuberculaius 

 ^ o -" i Gray. Brazil. (Fam. Reduvudae.) 



terous family, Membracidae (Fig. 



283), assumes the most extraordinary 



shapes. Both meso- and meta-thorax are well developed. 



former is remarkable for the great size of the scutelhun ; in 



some cases (Plataspides, Scutellerides) this forms a large process, 



^ For the structure and development of the Hemipterous trophi, see Mayer, Arch. 

 Anat. Physiol. 1874 and 1875 ; Mecznikow, Zeitschr. wiss. Zool. xvi. 1866, p. 389 ; 

 Geise, Arch. Naturgesch. xlix. 1, 1883, p. 315 ; Wedde, op. cit. li. 1, 1885, p. 113 ; 

 Mark, Arch. mihr. Anat. xiii. 1877, p. 31 : Smith, Tr. Amer. Phil. Soc. xix. 1896, 

 p. 176. 



(Antennae absent in the specimen 

 represented.) 



The 



