WERNER MARCHAND 151 



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 par- 

 takes of the color of the food ingested. The color is pale brown when 

 the food consists of the wet muck in which crustaceans and minute 

 forms are sought. As a result of feeding on blow-fly larvas and angle- 

 worms, the young Tabanus assumes a variegated color. The intes- 

 tinal tract then appears tinted with green, yellow, brown, and red 

 particles of the food. 



In one set of larvas, as Mitzmain says, "The origin of cannibalism 

 as an acquired 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 v;hich they might have 

 obtained from the surrounding creek water. Apparently they lived 

 together amicably with their bodies compressed against the glass 

 dish and the bit of filter paper. A live angleworm was placed in the 

 glass dish while the resting larvae were observed with a lens. The 

 worm was not placed in the immediate vicinity of the mass of larvae, 

 but nearly 4 cm. distant. The presence of the food appeared to act 

 as a stimulus. No movement was made towards the worm, but each 

 larva appeared to become greatly excited and began to prod the 

 larva nearest to it and to nip its neighbor's appendages; several 

 instances of laceration were noted. This doubtlessly marked the 

 beginning of systematic cannibalism. From this cause, 39 of the 

 365 larvas kept in the large glass dish were destroyed within four 

 days. Four dead bodies were recovered. Upon another occasion 

 the extent of cannibalism was much more marked. A lot of 415 

 larvae which hatched on November 12, 1912, was placed in a deep 

 glass dish with moist lake-beach sand, and fed daily on angleworms. 

 Each morning it was observed that only about one-half of the worms 

 supplied the previous day were eaten, so that with the daily fresh 

 supply more than enough food was present. Another lot of 300 

 larvae, the same age as the preceding, was kept in individual glasses 

 under similar conditions. On December 6, counts were made of the 

 survivors in the large glass dish. Thirty-five larvae remained, of 

 which eighteen were the maximum size, eleven were a little more than 

 one-half this size but equal to the largest found in the individual 



