58 
Genus 
STOMOXYS, Geoffroy. 
Stomoxys calcitrans, Linn. 
Plate 29. 
The similarity in size between this species and the House-fly 
{Musca domestica, Linn.) sometimes causes Stomoxys to be mistaken 
for the latter, with the result that the House-fly is occasionally 
supposed to be capable of biting. Apart from points of difference 
afforded by markings, however, Stomoxys, not to mention other struc- 
tural differences, can always be recognised by the little black, rigid 
piercing proboscis, which, as shown in the plate, when not in use 
projects horizontally in front of the head, whereas the fleshy, non- 
biting proboscis of the House-fly is normally carried drawn up into 
a cavity on the under side. The sexes of the present species can be 
distinguished by the front (space between the eyes) in the male 
being scarcely more than half the width of that in the female. 
Stomoxys calcitrans, which is the only European species of its 
genus, and, like Hcematobia stimulans, Mg. (Plate 30, Fig. 1), plagues 
both men and cattle, is common and generally distributed in the 
British Islands in summer and early autumn, and especially abundant 
in England in August and September, when it may often be seen 
sitting about in numbers on rails and gates in pasture-fields. The 
Museum series contains specimens from many different localities 
between and including the Southern Sutor, Cromarty, N.B., and South 
Devon. The dates of capture range from May 27th (Folkestone 
Kent) to October 3rd (Staines, Middlesex). 
With reference to this and the following species {Hcematobia 
stimulans, Mg.), Colonel Yerbury writes : — " These are common 
species in the Thames Valley ; 5. calcitrans was abundant, too, at 
Newmarket in October, 1905. The amount of pain produced by 
the bite of a Dipteron probably depends upon the idiosyncrasy of 
the person bitten ; to the writer, however, the bite of these two 
