( xxx vi ) 



was raised and lowered gently, and I could also make out the 

 brilliant white halteres in motion upwards and downwards. 

 When the abdomen was raised the halteres were depressed 

 together. I really think their association with ants is not 

 accidental. I got two or three pairs, and have been trying 

 to induce the females to oviposit on stale fruit, but without 

 success. I cannot account for the death of so many ants. 

 Hundreds of a Pheidole were running about, in many cases 

 carrying off dead Cremastogasters, with little or no molesta- 

 tion. I do not for a moment think the Pheidoles, numerous 

 though they were, could have caused the slaughter. I am 

 inclined to think the ants must have come from a ' foul ' 

 brood. I have put up a lot in spirit for examination, and am 

 keeping the nest under observation. They are still in the 

 same place, and the little flies are still busy in their curious 

 and rather unpleasant way." 



Dec. 29, 1917. — •" I have been laying traps for Harpagomyia 

 ova in the form of bits of calabash with water placed in the 

 hollow stem of the ant tree. I've got hosts of larvae of 

 different sorts, but four have outstripped all the others — great 

 red forms with white undersides which are predaceous on the 

 others. I feel sure they are Toxorhynchites ; I think the 

 other larvae are Stegomyia." 



Mr. Donisthorpe said it was of the greatest interest that 

 Mr. Farquharson had observed in S. Nigeria the same extra- 

 ordinary phenomena that Mr. Jacobson had first discovered 

 and described in Java. He stated that the behaviour of the 

 gnat as described by the two observers, although on the 

 whole similar, differed slightly in some respects. Jacobson 

 records that the Dipteron stood in the track of the ants, and 

 that when an ant ran between its legs it supplicated for food, 

 and was then fed as described by Farquharson. During the 

 process the wings of the gnat were so rapidly vibrated that 

 the nervures of the wings did not appear in photographs 

 taken of them while feeding. Jacobson had discovered and 

 figured the larva and pupa of the Harpagomyia. He says, 

 however, that the eggs, which lie does not figure, are laid in 

 branches of trees which the Cremastogaster had deserted on 

 account of their having been flooded by rain. The eggs may 



