260 Arthropoda. 



2. Water-bugs (Hydrocores) have short antennBB and a short proboscis ; 

 they live in water, -which they are, however, able to leave, in order to fly in the 

 air. AH are predaceous. Of forms f oimd in England, the Water -scorpion 

 (Nepa), belongs here, a flat, darkly-colom-ed insect, which is very common, 

 crawling about at the bottom of fresh water ; the front legs are prehensile, 

 the tibiae can be folded into grooves on the femurs, posteriorly there are 

 two filiform grooved processes, which together form a tube (the respiratoiy 

 tube), at the base of which lies a pah- of stigmata : also the Water -boatman 

 (Notonecta) with long, outwardly directed hind legs, covered with setse on the 

 tibise and tarsi ; these are swimming organs. 



3. Lice (Pediculidse), a small group of ametabolous parasitic Insects, are 

 probably to be regarded as peculiarly modified Heteroptera. The head is narrow, 

 with short antennse, and an ocellus on each side ; the suctorial apparatus, which can 

 be completely withdrawn into the head thfough an opening at the tip, consists 

 essentially of a short, thick tube, provided at the end with a few hooks, through 

 which a second thinner tube, the actual sucking tube, can be protnided ; the 

 more exact structure of the latter is not definitely known. The legs, which 

 are short and strong, end in chelae ; the tai'sus, consisting of one joint, beai's a 

 very powerful claw, which bites against a process arising from the lower end of 

 the tibia. Wings are altogether absent, the abdomen is large, broad, and 

 tough. The large eggs (nits) are stuck on to the hairs of the host. 



,1 2 3 



Fig. 216. 1 Cimex leotularius. 2 Pediculua capitis. 3 Phthirius pubis. All 

 enlarged. — After Tasohenberg. 



Lice only oocm- upon Mammalia, living as stationary parasites upon the skin, 

 sucking the blood; they grasp the hair by means of their legs. The follow- 

 ing species occui- on Man : Pediculus capitis and P. vestimenti, which are 

 very similar, the former living exclusively in the hair of the head ; the latter 

 on the naked portions (or, more coiTectly, the sparsely hairy), of the body ; also 

 Phthirius pubis on the hairy portions of the body, with the exception of the 

 head (in the hair of the pubic region, the beard, etc.), distinguished by the great 

 breadth of the thorax and abdomen. Other species, on domestic Mammalia. 



Order 3. Neuroptera. 



The Neuroptera are liolometabolous_ Insects^ witli four 

 similar, ttin wings, and biting mouth-parts. The 

 antenuEe are usually multiarticulate ; in some, the mouth-parts are 

 well developed ; in others, rudimentary. The prothorax is freely 

 movable ; the wings in some are closely veiaed, like those of the 

 Libellulidse ; in others, there are fewer veins. The larv® are pro- 

 vided with legs, but in other respects, are very diverse. The pupa 

 is peculiar in seeking a convenient spot for the completion of 



