424 Annals Entomological Society of America [Vol. V, 
tinctly smaller, circular, and from 4 to 6 times as far apart. (See 
Fig. 8.) Larval stage usually lasts 15 to 21 days, but may be extended 
under unfavorable conditions up to 80 days. 
Pupa: Bright reddish brown to chestnut brown in color, and nor- 
mally 6 mm. long; precisely similar to that of Musca domestica from 
which it may be distinguished by the plates in the same manner as the 
larva. In summer the adults usually emerge in 9 to 13 days after pupa- 
tion. (See Fig. 9.) 
Adult: Normal length about 7 mm., rather more robust in shape 
than either of the foregoing, darkish grey. Thorax with 4 conspicuous 
blackish longitudinal stripes. Abdomen without ochraceous-buff 
patches but dotted with clove-brown, the spots usually more conspic- 
uous in the @. Vertex 1 in o&, and 4 in @ the width of the whole 
head. Proboscis shining black, projecting horizontally in front of the 
head, visible from above when not feeding. The end of the 4th longi- 
tudinal vein bent up, but not so much as in Musca domestica. (See 
Fig. 7.) A biting fly, both sexes suck blood from human beings as well as 
from cattle, horses, etc. Common about farmyards and stables, and 
common in houses near such places, especially on dull days. This 
accounts for the old saying in the country districts, that it is a sign of 
rain when the flies bite. 
External Mouth Parts. 
Unlike some of the other well known Blood-Sucking Diptera 
the male of this species feeds also on blood, and I have been 
unable to determine any difference between the mouth parts of 
the two sexes of Stomoxys calcitrans. The following description 
will therefore apply equally well to male or female. The exter- 
nal mouth-parts consist of maxillary palpi and the proboscis. 
(Plate XXXIV, Fig. 1. mxp. and pr.) Maxille proper and man- 
dibles are not found, the proboscis consisting of the labrum, 
hypopharnyx and the labium. 
The maxillary palpi consist of a single segment and are 
approximately one-fourth the length of the proboscis. 
The proboscis, in a resting position, extends horizontally 
below the head and may be plainly seen projecting for about 
one-third of its length in front of the head. In this position 
its base is closely applied to the lower part of the head in the 
ventral groove, but when extended it will be observed that its 
attachment to the lower chitinous skeleton is membranous, 
except for the two strong apodemes. (ap. in Figs. 1, 2 and 4, 
Plate XXXIV.) 
The maxillary palpi are attached to this membranous cone, 
and do not, in any part, enclose the proboscis. The proboscis is 
