208 DISPERSAL OF PARASITIC EGGS 



distance they may traverse in their first flight after feeding. 

 In the experimental cage I was only. able to demonstrate this 

 up to a distance of three feet." When they have finished feeding 

 flies usually walk a short distance away to a convenient dry 

 spot, or, especially if disturbed, they fly off to the nearest place 

 of safet)'. They generally do not fly to a great distance under 

 such circumstances. Occasionally eggs which have been rubbed 

 off may again adhere to the fly. Xicoll showed that the longest 

 interval after which eggs were found adhering to flies was about 

 three hours. 



" The possibility of flies in this way contaminating food was 

 demonstrated by allowing some to feed on faeces containing eggs 

 of Hyvienolepis dimimita, and subsequently affording them access 

 to some moist sugar placed at the other end of the experimental 

 cage. After 24 hours the sugar was examined and found to 

 contain a few eggs. Now, as has already been shown, the eggs 

 of Hynienolepis dimimita are too large to be ingested by the fly, 

 so that in this experiment they must have been carried on the 

 legs or body." 



Feeding experiments zvitJi larvte. 



LarvK w^ere allowed to feed on ripe segments of Ticnia 

 serrata, and some of them were examined from time to time. 

 In some the ova were found but in every case broken. Flies 

 which hatched did not contain eggs or larvae of the parasite. 

 Larv.ne allowed to feed on dog faeces containing mature female 

 Toxascaris linibata, and on horse faeces containing female Ascaris 

 viegaloeephala with numerous eggs did not show eggs in their 

 intestines. Nicoll, therefore, concludes from these experiments, 

 which were repeated several times, " that the eggs are not trans- 

 mitted through the larvae to the fly." He points out that these 

 results are " entirely at variance " with the already quoted obser- 

 vation of Stiles in the case of Ascaris Innibricoidcs. 



' WihV fiies. 



Nicholls (191 2) in St Lucia made observations on Li)nosi?ui 

 punctipennis, which he considers as " by far the most objection- 

 able" of all the flies he investigated "as on every occasion on 



