EXPLANATION OF PLATES. 261 



Plate XVII. 



Upper portion. 

 Fig. i. — Phthiritis inguinalis, ^ , 20. 



ths., great thoracic spiracle — here apparently prothoracic. 

 1 a.s., 2 a.s., 3 a.s., 4rt.s. , 5 a.s., 6a.s., spiracles of the 1st to 

 the 6th abdominal segments, respectively, seen through the 

 body, rendered very transparent for the purpose. 

 r.L, r.l., r.l., r.l., rudimentary abdominal limbs, the true 

 limbs belonging exclusively to the thorax. The position of the 

 stomach, with partly digested food (blood), three immature 

 ova, etc., are also seen. The extremities of the anterior 

 limtjs will be seen to differ to a striking degree from those of 

 the posterior limbs. 



,, 2. — Termination of second limb, left side, of Hcematopinus siiis, 

 posterior aspect, tb., tibia ; trs., tarsus, said to be composed 

 of one joint only ; pv., pulvillus, (pulvillus, a pillow or cush- 

 ion). The spongy bodies at the end of a fly's foot are 

 " pulvilli" ; p., a. soft papilla, bearing two or three hairs ; 

 probably a delicate organ of touch; ad.c, ac^.c, adductor 

 muscles of the claw ; s.b., " sesamoid bone " of the adductor 

 muscle. 



,, 3. — Second limb of Phthirms inguinalis. The same letters 

 indicate corresponding parts. The dotted line indicates 

 point of fusion of tibia and tarsus. 



4. — The eye in Mr. Harkness's case of Phthiriasis palpebrarum. 



5. — Egg (containing a foetal louse) and an egg shell (with lid 



detached, and puckered internal membrane) mounted in 



glycerine, from the same. 



J) 



Lower portion. 

 ,, 6. — Melophagus ovinus, sheep tick, 3' , seen in the ventral aspect, 

 X 10. 



ee. , eyes (position of) ; at. , at. , position of antennae ; r. , 

 rostrum ; pp. , palpi ; 1 ab, dorsal portion of first abdominal 

 segment ; 1 abx , ventral plate of same segment ; v. , vent 

 and orifice of external organs of generation; pt.s., protho- 

 racic spiracle (position of) ; mt.s., methoracic spiracle ; 1 a.s. , 

 2 a.s., 3 a.s., 4 a.s., 5 a.s., position of the 1st to the 5th 

 abdominal spiracles, respectively ; 6 a.s., spiracle of 6th ab- 

 dominal segment. 



,, 7. — Sketch, showing method of using a mounted needle in 

 dissecting a fly. 



Plate XVIII. 

 Fig. 1. — Nyderibia, ^ , from Flying Fox. 

 g.s., genital segments, coalesced. 



,, 2. — Outline view of ? , Nyderibia, from Flying Fox. The same 

 letters are used as in figure 6 of preceding plate (sheep tick) 

 to indicate corresponding parts. 



New Series. Vol. L 



i888. T 



