180 THE EARLY STAGES OF TABANID^ 



Graber, as Paoli mentions, gives his larva (in the figure) erro- 

 neously, only ten segments, while it is known that the larvae of Diptera 

 have fourteen segments, of which the last one is vestigial. 



The largest specimens of the larvae examined are, when completely 

 extended, 30 to 32 mm. in length. The body is fusiform (Plate 10, 

 Fig. Ill), the color a dirty yellowish white, the head is elongate, 

 retractile; the three thoracic segments do not present any peculiari- 

 ties. The first seven abdominal segments are furnished each one 

 with eight papillae, arranged all around the anterior third of each seg- 

 ment, which consequently in cross-section presents itself with eight 

 prominences arranged like the corners of a regular octagon. These 

 papillae are retractile, and each of them is furnished at the tip with 

 numerous strong booklets. The larva moves in the mud and among 

 the algae, in addition to making worm-like movements due to the con- 

 tractions of the subcutaneous muscular stratum, also by protracting 

 and retracting the fifty-six papillae which in this way form a support 

 and assure to the larva its locomotion. The eighth segment bears 

 on its ventral side a thick sulcate prominence, in the middle of which 

 the opening of the anus is situated. Anterior to this prominence a 

 large lip-like expansion is formed, with numerous strong booklets 

 which are curved forward at the free margin. Behind the anal 

 opening the eighth segment is narrow and curved upwards; he 

 ninth segment is short, cylindric, thin, more or less retracted into the 

 inside of the eighth, bearing at its extremity the rudiments of the 

 tenth, in which the two stigmata open. 



Paoli, after thus briefly describing the larvae, adds that when dis- 

 turbed by contact or pressure, they undergo contortions in every di- 

 rection, making a sound like the crackling of small electric sparks. 

 They feed on animal matter and ferociously attack small larvae of 

 other aquatic insects, and also devour one another; when they are 

 attacking one another the crackling sounds are heard repeatedly. 

 For the description of Graber's organ in these larvae see page 29 and 

 following. 



Tabanus sp. No. 13. — Maxwell-Leffroy and Hewlett (1909) give, on 

 a colored plate, illustrations of the egg mass, young larva, full grown 

 larva, pupa, and an ichneumonid parasite of an unidentified Indian 



