156 Journal New York Entomological Society, [Vol. xxv. 



tenth segments, two pairs on each of these segments, forming two 

 pairs of rows, one lateral and one ventral. On the dorsal side of the 

 second segment a pair of black ocelli are visible which in reality lie 

 not on the upper surface of this segment but underneath it on the 

 upper side of the pharynx which, with the head and mouth, is re- 

 tractile. The eyes are moved forwards and backwards with the 

 pharynx, so as to lie apparently sometimes in the second and some- 

 times in the third segment of the body. Similarly located at the hind 

 end of the body and situated on the dorsal side of the tenth or 

 eleventh segment lies the " organ of Graber," to be spoken of later, 

 visible as two small black dots. The twelfth segment is terminated 

 obtusely in the newly hatched larva (Plate X, fig. 4).- 



First Molt. — Only a few hours after hatching the larvae, placed 

 in water, begin to molt. The act of molting was observed repeatedly 

 and the presence of larval skins in the water indicates that it has 

 taken place. Plate X, fig. 5, shows an individual in the act of molting. 

 This first molt has not been noticed in Tabanid larvae, nor by Mitz- 

 main, who has given some attention to the subject of molts. 



Description of Larva After First Molt. — After the first molt the 

 larvae are more slender and slightly longer than before. The. prolegs 

 are now more in evidence, protruding at right angles from the body- 

 surface, and the crawling movements become much more energetic 

 (Plate X, figs. 7 and 8). In the structure of the head no important 

 changes could be noticed; of these structures and of the mouth parts 

 and antennae, a more detailed illustration is given (Plate XI, fig. 3). 

 Hart gives as difference between Chrysops and Tabanus larvae the 

 relative length of the last and second-to-the-last antennal joints; this 

 character could so far not be verified with certainty in this young 

 stage. A very good character which seems to separate at least those 

 Chrysops and Tabanus larvae which I had under observation is found 

 in the tracheation. The main tracheal trunks of the young larva of 

 C. callidus are relatively slender and narrow, being between one 

 eighth or one tenth of the abdominal diameter in width, while in the 

 young Tabanus larva the tracheal trunks are of much wider diameter. 

 In the Chrysops larva, the diameter of the main tracheal trunks re- 

 mains the same throughout their entire length, while in Tabanus they 

 are much more inflated in the posterior half of the body than in the 

 anterior (Plate XI, figs, i and 2). 



