108 [May, 



different pressures sustained, when they were embedded in the host. 

 There are also differences in details of colour and in the form of the 

 mandibles similar to those which I have observed in other species of 

 Stjlopidae, and it is quite certain that minute characters in Sfylops and 

 Halictoxenus are not sufficient to sepai^ate species without the exami- 

 nation of more than single specimens of the $ or of the J sex. 



There are five tubes leading into the brood-chamber, as in all 

 Halictine Stylopidae that I have seen. 



The type was extracted from a specimen of H. xanfJiopus taken 

 this 3'ear on March 24th, on a tiower of Vlex, close to my house in 

 Devon. This is an extremely early date for the hibernated bee to be 

 abroad. The other was found in a bee captured last spring at a con- 

 siderably later date and only recently examined. Both these female 

 parasites contained ova very little developed, whereas usually the 

 9 HaJictoxenus examined in spring, after hibernation, contains fully 

 developed triungulin larvae. 



This species is named after Mr, G. Arnold, who was a most active 

 collector and student of oui* Aculeata, before his departure abroad. 



In my descriptions of Halicfoxenus {ante p. 74) I find that I 

 carelessly misread the numbers on the divided millimetre scale, by which 

 the length and breadth of the cephalothorax was measured, so that in 

 each case these measurements are about one-quarter of a mLllimetre 

 too great. The following table of species will sufiiciently correct the 



error : — 



Halictoxenus $ $ . 



1 (2) Large species ; width across the spiracles '9-1 mm.: length from hind 



margin of spiracle to middle of front margin of head 'S-'Q mm. Dark 

 brown or blackish basal area extending forwards beyond the line of 

 the spu'acles arnoldi. 



2 (1) Smaller species, not reachiDg 9 mm. in width, 



3 (6) Pale discal spots are present between the line of the spiracles and the 



opening of the brood-chamber. 



4 (5) Width about '8, length about -6 mm. ; a dark suffusion extends from the 



base to about the line of the spiracles cylindrici. 



5 (4) Width about '6, length about -40 mm, ; the pale discal spots midway 



between the opening of the brood chamber and the line of the 

 spiracles are more conspicuous than in the preceding . . spencii. 



6 (3) Pale spots situated near the base of the cephalothorax, behind the fine of 



I he spiracles. Width about -66, length -56 mm tumvlorum. 



Paignton. 



^J9nn8^^, 1918. 



