VIII, B, 3 Mitzmain: Biology of Tabanus striatus Fabricus 203 



it is in the case with Stomoxys and the dung flies. The Tabanus 

 larva requires a long rest after a sufficient meal is taken, A 

 2-day-old Tabanus is capable of devouring 2 half-grown larvae 

 of Stomoxys in twenty-five minutes. In one instance a full- 

 grown Stomoxys larva was destroyed in exactly twenty minutes. 

 Here the attack on the Stomoxys was made through accidental 

 collision, the Tabanus instinctively thrusting out its mouth and 

 tentatively taking a bite. It apparently became greatly excited 

 (this was its first meal), and, thrusting its head into the body of 

 the Stomoxys larva, commenced to probe by twisting its head 

 rapidly. In less than a minute the cuticle was broken through 

 and an ample slit was made through which the entire head was 

 buried in the body of the victim, whereupon an energetic 

 gouging took place. The Tabanus worked through the cephalic 

 third of the body upward to the head, then worked in the other 

 direction on the lower two-thirds. This gouging was continued 

 until the Stomoxys had become completely eviscerated, during 

 which time the head of the Tabanus kept steadily probing, 

 twisting its pharynx from side to side, and pushing forward 

 with its rostrum until the Stomoxys larva was completely de- 

 voured with the exception of the cuticle. 



The full-grown Tabanus larva does not wait for its food, as is 

 the tendency in the young stage, but actively pursues its prey. 

 When an angleworm is seen, perhaps 2 millimeters distant, the 

 elastic head capsule of the larva darts forth, curves its claw-like 

 hook about the worm's body, and, with its head curled under its 

 struggling prey, retreats quickly into the sand until all but its 

 cephalic end is hidden. It begins to feed then, devouring in 

 twenty minutes an angleworm fully four times its own length. 



The intestinal tract seen through the hyaline cuticle soon 

 partakes of the color of the food ingested. The color is pale 

 brown when the food consists of the wet muck in which Crustacea 

 and minute forms are sought. As a result of feeding on blowfly 

 larvae and angleworms, the young Tabanus assumes a variegated 

 coloration. The intestinal tract then appears tinted with 

 green, yellow, brown, and red particles of the food. 



In one set of larvae the origin of cannibalism as an ac- 

 quired habit was observed. This was seen in larvae which 

 had been kept together for four days since their birth. Until 

 that day no food was offered them except that which they 

 might have obtained from the surrounding creek water. Ap- 

 parently they lived together amicably with their bodies com- 

 pressed against the glass dish and the bit of filter paper. A 



