FAMILY TABANIDAE: EARLY STAGES 299 



first one larva wriggles out and very soon afterwards the others emerge 

 and the mass is transformed into a collection of larvae struggling to 

 free themselves ; they drop singly or in heaps into the water or wet 

 mud, and quickly bury themselves out of sight. The recently hatched 

 larva is almost pure white, and both ends are, as a rule, pointed. 



The body of the mature larva is cylindrical, tapering at both ends, 

 and consists of eleven segments excluding the head ; its skin may be 



blotched or streaked in the form of stripes or bands. 



T>U j-u i j ^u u i A. u External structure 



The antennae are three- jointed, the basal lomt being 



of mature larva, 



short, and are attached to the anterior angles of the p| a t e XLII 



head just above the palpi ; a bunch of stiff spines, either 

 short or moderately long, is situated just above each antenna and on each 

 side of the labrum. The segments of the body are whitish or striated, 

 and the prothorax has a groove on its ventral surface. Each segment of 

 the abdomen has a Y-shaped group of punctures and is encircled 

 anteriorly by a horizontal ridge beset with fine hairs. There are two 

 prominent fleshy tubercles at each lateral angle, and four, arranged in 

 pairs, on the ventral surface. The last segment has a bilobed anal 

 prominence bounded posteriorly by a semicircular ridge covered with 

 hairs. The vertical stigmal plate is situated at the apex of a conical 

 retractile prolongation, the syphon tube. 



The mouth parts of the larva are adapted for seizing the prey, and 

 constitute a very formidable apparatus. The essential organs are the 



mandibles and first maxillae, and of these the former 



The mouth parts 

 are the most powerful weapons. Each mandible is a 



stout rod of chitin, slightly expanded at the base, to which the muscles 

 are attached, and narrowed distally to a blunt point ; the rod is curved 

 downwards and forwards, and is armed on its concave border with many 

 coarse serrations. The maxillae are similar in shape and general dispo- 

 sition, but are smaller and less heavily pigmented, and are more pointed. 

 Both pairs of appendages can be thrust out of the head in a downward 

 and forward direction when the larva attacks its prey, by means of the 

 protractor and retractor muscles attached to the bases of the rods. One 

 sometimes becomes unpleasantly aware of the existence of these organs 

 when handling the larvae, as they are used in defence as well as in 

 attack, and are capable of inflicting a sharp nip, though they do not 

 draw blood. The maxillary palps are simple and two-jointed, the distal 

 joint being much smaller than the proximal one. The dorsal and distal 

 extremity of the head is produced forwards as a short and fleshy 

 labrum. 



