376 MB. STANLEY HIRST ON 



than in P. tarscdis, resembling that of P. cestivus in this respect. 

 First tarsus produced beyond and above the claw, but apparently 

 not so strongly as in P. tarscdis. 



Striated sensory (" olfactory ") hairs on first tarsus rather 

 similar to those of P. tarscdis ; they are four in number, all of 

 them being more or less club-shaped ; the one situated near the 

 distal end is very short and slender, the next is the largest, being 

 rather stout, close beside it there is another slender but not very 

 short sensory hair, the sensory hair nearest the proximal end of 

 the tarsus is very short and slender. Second tarsus with a short 

 but fairly stout sensory hair near the proximal end ; the claws of 

 this leg are distinctly bifid. 



There is an unusually stiff bristle on the dorsal surface of the 

 first leg (especially well developed in examples from Lyperosia, 

 irritans ( = Hcematobia serrata)). 



Length of body 205-225 ll ; width 110-140 ll. 



Habitat. Pseudoparasitic on Musca clomestica, (slides in collec- 

 tion of Laboratoire de Parasitologic, Paris) and Stomoccys ccdcitrans 

 (the specimen from the latter was collected by Dr. J. Burton 

 Cleland, and therefore is presumably Australian in origin). Also 

 numerous specimens (reddish in colour) found on an English 

 specimen of Lyperosia irritans. 



Prof. T. Harvey Johnston and M. J. Bancroft mention in their 

 paper on the life-histories of Musca australis (M.fergusoni) and 

 M. vetustissima (Proc. Roy. Soc. Queensland, 1920, xxxi. footnote 

 on p. 183) that "These flies may be parasitised by larval mites, 

 a red one probably Acarus muscarum Linn., and also a minute 

 whitish species." The latter is probably the species identified as 

 P. americanus in the present note. 



Pygmephorus americanus var. socotrensis, var. nov. 



5 . Very like the typical P. americanus in most respects, but 

 with the sensory (striated) setse on the tarsi of the first and second 

 legs different in shape, the largest one on the first tarsus being 

 considerably elongated and cylindrical, whereas in /\ americanus 

 (typical form) it is club-shaped. The sensory seta of the penul- 

 timate segment of the second leg differs in a similar manner. 

 The paired oval structures situated near the front of the cephalo- 

 thorax are placed close together as in P. americanits, but are 

 constricted in the middle (perhaps differences like this are merely 

 due to the presence of air or gas in the preparation). Pseudo- 

 stigmata globular as in P. americanus. There is a stiff dorsal 

 bristle on the second free segment of the first leg, much as in 

 P. americanus. 



Measurements. Total length 210 ll ; width 125 ll. 



Hah. Musca clomestica : Socotra. A single specimen found on 

 a dry example of a fly from that locality. 



