12 



FEEDING OF THE ADULT 



Suitable moist food is a prerequisite to normal oviposition. The 

 adults lack the power to soften desiccated food, and because of the 

 structure of the mouth parts can not do more than " lap " and suck 

 semiliquid or liquid materials. Oviposition does not occur, or takes 

 place infrequently, when the supply of proper food is insufficient. 

 Flies given water alone do not lay eggs. Water is frequently sought 

 by the adults, which were often found in the laboratory about drip- 

 ping faucets. 



Murtfeldt (53, p. 17b), one of the few who have considered the 

 matter of adult feeding, stated that " It will sip a little at sweets, 

 * * * while the odor of smoked meats speedily summons it." 

 She reported that the flies were first noticed in the packing houses 

 around vats of yellow wash — a mixture of glue, rye flour, coloring 

 matter, and water. Mote (51, pp. 31b~315), as previously stated 

 (p. 5), found that the adults live longer on putrid beefsteak than on 

 ham, bacon, or cheese. Lodge (bh P> b^6-b87) stated that peptone, 

 both moistened with water and mixed with bread, and sometimes 

 containing maggots, attracted many adults of P. casei. She found 

 a casein bait effective. Sakharov (67) reported that these flies can 

 feed on many substances, even the nectar of flowers. 



Although adults live without food for several days in warm 

 weather, as shown elsewhere (Table 8), nourishment prolongs the 

 life of both sexes, especially of the males. This appears to be 

 due to the fact that fed females oviposit and the consequent drain 

 upon their vitality results in earlier death. In one trial about 200 

 unfed and unwatered adults were given thin slices of juicy ham; 

 this was immediately covered with the flies, lapping at the surface 

 with rapid, shifting pecks, like chickens eating scattered grain. 

 Water-soaked cotton was then introduced, but failed to lure more 

 than a few flies from the meat. Fresh pieces of cheddar cheese were 

 eagerly attacked by them, but once the surface of these foods became 

 lapped dry no more nourishment could be obtained. 



Water-soaked cotton attracted many flies when offered to a large 

 number of them which were thirsty. Some were observed to draw 

 drops of water away from the main supply and then to suck it up 

 from the glass; others inserted their proboscides through the surface 

 film of the main supply. In one experiment newly emerged adults 

 which were fed upon fresh cheese, and were thereby enabled to re- 

 produce, soon became unable to obtain food on account of the hard- 

 ening of the cheese, but began feeding again a few days later, after 

 their progeny, with ability to soften the cheese, had reduced it to a 

 paste. 



Bachmann (9) stated that the adults regurgitate droplets of liquid 

 food, after the manner of house flies, but the writer has not been able 

 to observe this. 



The odor of putrid meat is attractive to cheese-skipper adults. 

 Cultures of larvae in putrid ham unfailingly attract most of the 

 adults in the room, and the same is true of strong-smelling cheese, 

 decaying beef, and freshly cured ham. Adults confined with semi- 

 liquid, putrid beef gorged themselves with it until they were notice- 

 ably distended, and oviposition was observed to be profuse. 



