378 Transactions of the Society. 



Kramer's species, Pygmephorus spinosus, was an adult creature, 

 and a perfectly good and very interesting species. With regard to 

 the other Acarus, which Kramer called Lahidophorus talpse, it 

 appeared probable that this really was an immature (hypopial) 

 form. 



Before proceeding further, I may as well, for the sate of clear- 

 ness, remind my readers what a Hypopus is. I trust that I 

 have elsewhere * satisfactorily shown that the hypopial stage is one 

 assumed by some of the nymphs of certain Acari for the purpose 

 of enabling them to endure more adverse conditions of heat and 

 drought than the ordinary nymph can survive, and thus adhere to 

 insects, &c., which may be exposed to hot sunshine, &c., and be 

 transferred by them to new localities ; whereby the distribution of 

 the species was ensured ; and that the hypopial stage occupied the 

 period between two ecdyses in the ordinary nymphal life-history, 

 and also, I think, showed that some Acari which were adult sexual 

 forms assumed a very close resemblance to the true Hypopus, 

 except in the mouth-organs, with the object of ensuring distribution 

 in the same manner as the hypopial nymphs. 



What rendered it almost certain that Labidophorus talpse was 

 a hypopial nymph, was that in 1879 Dr. G. Haller, then of Bern, 

 discovered, parasitic upon the squirrel, an Acarus of which the 



Plate XI. 



Fig. 13. — Glyciphagus Crameri, adult male ; 1st right leg from without X 380. 



14. — „ „ „ 2nd left leg from withia X 450. 



15.— „ „ „ 3rd „ „ X 450. 



16. — „ „ hypopial nymph ; 1st tarsus. 



17. — „ „ „ „ 3rd left leg from without. 



18. — „ „ „ „ 4th tarsus, showing the two 



claw-like hairs turned upward. 



19. — Glyciphagus Crameri^ hypopial nymph, posterior apparatus for holding 

 hairs on the ventral surface, (a) anus ; (6) channel wherein the hair 

 lies ; (c) large lips or wing-like processes, which lie over the hair, 

 and usually overlap each other a little when there is not any hair 

 there (they are not drawn so for the sake of clearness) ; {d) chitinous 

 plates on the inner side of the lips ; (e) chitinous band near the 

 edge of the inner surface of the plate, with hard transverse ridges 

 on its inner side, which are only seen through in the figure from 

 the transparency of the chitin ; (/) circular chitinous plates with 

 radiating ridges on the under side of the abdomen ; (^) plate 

 sloping down, which serves to turn the hair away from the anus. 

 On the right side is indicated the retractor muscles of the 

 labia, &c. 



20. — Disparipes exhamulatus, adult female, dorsal view X 250. 



21.— „ „ „ „ ventral view X 250. 



22. — „ „ „ male, dorsal view x 350. 



23. — „ „ larva. 



* "The Hypopus question," Joum. Linn. Soc. — Zool., xvii. (1884) 

 pp. 371-94. 



