Tae MuicroscoricaL NeEws 
AND 
NORTHERN MICROSCOPIST. 
Nose 2g: MAY. 1883. 
THE ORAL ORGANS OF THE GAD-FLY. 
By J. B. PETTIGREW. 
N preparing a former paper on the Gnat and Mosquito, the in- 
terest excited by the examination of the complex oral organs of 
these insects led me to carry the investigation a little further, and 
to enquire how far they would bear comparison with those of other 
blood-sucking Diptera. 
The Gad-fly naturally presented itself as very convenient for the 
purpose, on account both of the size and of the clear definition of 
its sete, which render them readily available for microscopical 
purposes. 
Without attempting to point out the differences of structural 
detail which distinguish the oral apparatus of the various species of 
the family Tabanidz, I propose to give a short description of them 
as presented in the common grey Gad-fly—Hematopota Pluvialts. 
Fig. 37 is a drawing done under the camera of the organs of this 
insect as displayed in a prepared slide and amplified to twenty-one 
diameters. 
We have here a good example of a suctorial mouth, furnished 
with a full complement of organs, each of which is complete in it- 
self, and is adapted to a special purpose. It will be noticed that 
the setae are of four distinct kinds. They are all composed of 
clear amber-coloured chitine, are set closely together, and possess 
considerable strength and rigidity. The fifth organ, however, the 
labium, is remarkable for its extreme flexibility, rendering it, as we 
shall see later, capable of traversing a comparatively extensive area. 
Viewed together, these form a proboscis-like, downward prolonga- 
tion of the head in a direction at right angles to the axis of the 
thorax, with a thickened, somewhat bulbous extremity, caused by 
the position and shape of the /adium,; the setae themselves, when 
at rest, forming a slender body tapering to a blunt point and resting 
upon the cavity of the /adzum. Commencing anteriorly, the organ 
VOL. III. 
