VIII. B. 3 Mitzmain: Biology of Tabanus striatus Fabricus 209 



changes are due probably to a clearing process, in which the 

 larva indulges during the somnus preceding each ecdysis. 



After the second molt the fleshy protuberances functioning as 

 prolegs become reinforced with a slight cuticular ring at their 

 bases. The mouth parts at this stage are heavily chitinized. 

 The great hooks or mandibles show a marked serration of the 

 biting edge. The head projects more, exposing the dark brown 

 ocelli, which prior to the second molt are seen only through the 

 cuticle of the thorax situated nearly on the middle of the con- 

 cealed head capsule. 



The signs characteristic of the final molt are refusal of food, 

 restlessness, attempted migration, and finally burial in the sand 

 at the bottom of the jar. The body decreases slightly in length, 

 but the thickness remains the same. 



On the extremity of the abdomen tiny tubercles appear which 

 project more from time to time, becoming tapering and spike- 

 like. Near the caudal end of the abdominal segments, roots 

 of hairs appear. These at first resemble brown spots of pigment 

 and gradually lengthen into stiff brown hairs. The cuticle on 

 the body becomes stiffened and shingle-like at the joints of the 

 segments. The latter telescope less, and one can see numerous 

 particles of sand embedded in the joints of the segments. These 

 sand particles have been carried in during the telescopic move- 

 ments of the abdomen. 



After the fully developed larva passes through a period of 

 semidormancy buried in the sand, the skin is seen to be ridged 

 with cuticular plates. The head region is reinforced by stif- 

 fened cuticle, and the mouth orifice is closed by a plug of hard 

 rose-colored cuticle. This pigmented material lines the entire 

 pharyngeal sinus, plugging the mouth and the cephalopharynx. 

 The cuticular plug has a substantial fold which forms a slit for 

 the passage of the molting mouth. Caudally a similar imper- 

 vious mass closes the opening of the siphon. A cuticular collar 

 strengthens the base, and the connective tissue surrounding the 

 trachea of the tract of the siphon tends to contract. Then the 

 supports of the central trachea are gradually cast loose by a 

 gentle wriggling of the insect's body. About this time there 

 is a general wrinkling of the epidermis, the folds telescoping 

 upon each other, and the surface becomes parchment-like. 



Synchronous with the primary contraction of the segments, a 

 light pea-green suffuses the last 3 segments of the body. The 

 remainder of the larva changes to this color overnight. By 

 morning the abdominal segments have changed from green to 



