ON A PARASITIC GAMASID MITE. 383 



29. On a Blood-sucking Gamasid Mite (^Iclioronyssus ser- 

 pentiian, sp. n. ?), parasitic on Gouper's Snake. By 

 Stanley Hikst, F.Z.S.^ 



[Received April 30, 1915 : Read May 25, 1915.] 



(Text-figures 1 & 2.) 



It is quite probable that the species dealt with below is identical 

 with that to which Gervais gave the name Dermanyssus natricis 

 in the year 1844, but as there is some doubt on this point, I am 

 describing it under a new name. Gervais says very little about 

 the structure of his species, and the only account of it which is 

 at all complete is that written by Paul Megnin in 1884, who 

 created a new genus [Ojjhionyssits) for it. References to several 

 earlier papers and works in which this parasitic mite is mentioned 

 are given in Megnin's paper. Unfortunately he makes a serious 

 mistake in his description, stating that there is no ventral plate 

 (plastron) on the lower surface of the body, and that the 

 " oviducte" has the form of a longitudinal slit. It is quite clear 

 that he mistook the narrow geni to- ventral plate for the genital 

 opening itself. In reality, the genital aperture is quite normal 

 in apjDearance, being transverse and protected by the usual deli- 

 cate chitinous flap or operculum, which is joined posteriorly to 

 the genito-ventral plate. Ophionyssus natricis is mentioned by 

 G. Canestrini in his ' Prospetto dell' Acarofauna Italiana,' and 

 also by Prof. Antonio Berlese in his well-known work on the 

 Acari, etc. of Italy ; but these authors did not have the oppor- 

 tunity of examining specimens, and the latter expresses doubt as 

 to the validity of the genus, rightly considering it as probably 

 identical with Leiognathus Can. [= Ichoronyssus Kolenati]. 



It may be of interest to note that, in having two dorsal shields 

 and also minute intermediate platelets, the adult females described 

 below present a strong resemblance to the protonymph stage 

 of certain other species of Ichoronyssus (for instance, to that of 

 /. hacoti mihi). 



Genus Ichoronyssus Kolenati. 



Devnianyssus (ad part.) Gervais, in Ins. Apt. iii. p. 223 (1844) ; 

 Ichoronyssus Kolenati, Wien. ent. Monatschr. ii. p. 5 (1858); id. 

 Sitz. K. Akad. Wiss. Wien, xxxv. p. 173 (1859); Ophionyssus 

 Megnin, Bull. Soc. Zool. France, p. 109 (1884) ; Ophionyssus -{- 

 Leiognathus G. Canestrini, in Prospet. Acarof. Ital. part i. p. 121 

 (1885) ; Liponyssus of some recent authors, but probably not 

 that of Kolenati. 



* Published bj- permission of the Trustees of the British Museum. 



