70 THE EARLY STAGES OF TABANID^ 



Under ordinary conditions the head, which is small in comparison with the 

 body, reddish and semicoriaceous, appears conical; but when protruded for- 

 ward, it forms a sort of neck posteriorly. It is retractile to the extent that it 

 can disappear completely in the first segment. The front is protruded into a 

 fleshy mouthpiece which Perris assumes to be the labrum. To the right and 

 to the left of this a black horny linear piece is seen, which is curved anteriorly 

 and prolonged posteriorly into a rod, becoming more and more thinned out, which 

 is observed through the transparent tissues and which is inserted deep in the 

 first segment. These two rods are at first parallel, then somewhat diverging. 

 They serve, according to Perris, as places of attachment to the muscles which 

 move the head and the linear piece mentioned, which are the mandibles. Below, 

 two fleshy subconical pieces are seen, fused together at their base, of which the 

 inner is separated from the outer one only at the tip of the latter. The external 

 piece, which is a maxilla, is surmounted by a rather long palpus of two joints, 

 the first of these joints one and a half times as long as the second; the inner 

 piece is the lobe of the maxilla. Above, on each side of the head, opposite to the 

 base of the maxillae, a rather long antenna is situated, which appears to consist 

 of three joints, of which the first is very short, the second four or five times 

 longer, the third slender and about one-half as long as the preceding. 



This larva has, consequently, a protruded labrum, two horny serrate man- 

 dibles, two maxillae with their lobes, two maxillary palpi consisting of two joints,, 

 two antennae consisting of three joints, all extending beyond the head. 



The body is formed of eleven segments; the first, or prothorax, truncated 

 conical, is one and a half times as long as all the other thoracic segments, which 

 are slightly shorter than the abdominal segments. The first six of the latter 

 have eight fleshy and retractile protuberances, two dorsal ones distant from one 

 another, two on each side placed close together, and two ventral ones placed at 

 a distance from one another like the dorsal ones. These protuberances are of 

 great help to the larva when it starts to walk. In this act, the larva presses 

 the head against the surface on which it is to move and contracts the body, at the 

 same time retracting the protuberances; then, freeing the head and exserting the 

 protuberances which, all around, exercise a strong pressure, it pushes forward. 

 The last segment of the abdomen, which is somewhat rounded at the sides, is 

 rather suddenly and considerably narrowed down posteriorly, where it terminates 

 in a disk in the center of which a reddish vertical slit is observed with the aid 

 of a lens. At high magnification this slit is recognized to be a spiracle the lips of 

 which are transversely striated. In seeking for the remaining respiratory orifices^ 

 two of these oval and reddish spiracles are found at the posterior border of the 

 prothoracic segment, one on each side. Under the last segment, in its anterior 

 third, there exists a fleshy prominence, of the shape of an ellipsoid placed trans- 

 versely, and retractile; it is traversed by a longitudinal fissure or sulcus which 

 indicates the anus. This prominence also serves to aid locomotion. 



