VIII, B, 3 Mitzmain: Biology of Tabanus striatus Fabricus 219 



The incubation period has been determined to be from three to 

 five days. 



2. The behavior of the larva indicates that it is essentially an 

 aquatic form. The insect in this stage has been found to be 

 extremely cannibalistic. In some instances as high as 85 per 

 cent of the brood has been destroyed by this means. They 

 apparently prefer their kind to any other food; at least, there 

 is no diminution of the practice even when an abundance of 

 other food is present. There is shov^^n to be a marked diversity 

 in the development of larvae of the same age. The larval period 

 covers six weeks or longer. 



3. In the ecdyses of Tabanus striatus there are 3 distinct 

 molts; the final one, coming a considerable time after the 

 larva is full-grown, results in the unveiling of the puparium. 

 The puparium is formed beneath the molting skin of the full- 

 grown larva. This stage lasts from three to seven days, with 

 an average of five and one-half days, in the male; and from 

 four to nine days, with an average of six days, in the female. 

 In this period the male can be distinguished by the arrangement 

 of the short spines anterior to the terminal teeth of the abdomen. 

 These form a continuous serrated border of from 10 to 12 short 

 spines. In the female these spines occur in two groups of from 

 4 to 6 each. Evidence of development of the adult fly is had in 

 the changes of coloration visible through the puparium. 



4. The imago emerges through an opening formed by a dorsal 

 slit of the thorax and the fractured hood of the orbital region. 

 There is a definite clearing process upon emerging. In from 

 fourteen to twenty minutes after emergence the imago takes 

 fiight. 



5. The process of feeding in the female fly is described. Both 

 sexes have a lapping organ, in addition to which the female 

 possesses a distinct piercing organ. In the latter sex two 

 methods of procuring food are indicated. 



6. All of the draft animals of the Philippines serve as hosts 

 for Tabanus striatus. The carabao appears to be the host of 

 choice. 



7. The rain trees of this locality serve to harbor great num- 

 bers of resting horseflies. In considering methods of eradica- 

 tion, this fact should be considered. 



8. The following table gives an outline of the minimum days 

 required for the life cycle of flies of this species. From the time 

 the eggs are laid to the emergence of a female fly a period of 

 fifty-two days elapses. 



