﻿TACHINGIDES, NEAK GEIDAM, BORNU PROVINCE, NORTHERN NIGERIA. 197 



after the manner of house-flies. When completely at rest, the halteres are 

 motionless, but when the hind legs are moved or rubbed together, the halteres 

 are moved up and down, slowly enough to be easily followed by the eye. 



On one occasion a fly was seen to feed upon the abdomen of another. The 

 biter was a female, the bitten fly a male, which had been on its back for some 

 time, unable to rise, and so appeared in a weakly condition, but was not dead. 

 The female inserted the proboscis into the abdomen on the ventral aspect, and 

 worked it backwards and forwards, never quite withdrawing it, but again pushing 

 it in in another direction. While this was in progress, a second fly appeared, 

 and attempted to obtain a feed from the same male, but was apparently driven 

 off by the female spreading out her wings and legs. 



In the evening the flies were very hungry, constantly feeling the sides and 

 bottom of the bottle with the unsheathed proboscis. A bit of fairly dry branch 

 of a tamarind tree, and two leaves of the ebony tree were put into the bottle (A). 

 The flies rarely alighted on the leaves, and only a few settled on the twig. 

 One was seen trying to insert its proboscis between the bark and wood of the 

 twig, the head of the fly being in a tremulous condition, suggesting supreme effort. 



While watching a female at rest on the floor of the bottle, I noticed a violent 

 contraction of the abdomen, starting from the thorax, and immediately a white 

 larva was extruded. The fly remained on the spot for a few minutes, and then 

 flew away. The larva was quite white, the " tumid lips " being absolutely trans- 

 parent, resembling bubbles of water, and in a very short time regular rhythmic 

 contractions commenced, starting at the posterior end. The larva was fixed to 

 the floor, and could not be displaced by shaking the bottle. At the end of about 

 ten minutes, the larva was dry, but was still fixed by the tumid lips, the anterior 

 end moving from side to side slightly. Shortly afterwards, it could be displaced 

 by shaking the bottle, and passed into a condition of perfect quietude, exhibiting 

 no movement whatever. 



About 4.30 p.m., the fresh liver of a fowl, attached to a piece of string, was 

 lowered into bottle (A). For half an hour the flies took no notice of it, although 

 chey seemed to be frantic in their efforts to obtain a feed on the floor of the 

 bottle. Then one fly, and others afterwards, settled on the liver, waited for a 

 minute or so, and then inserted the proboscis into the liver, driving it steadily in 

 as far as the bulb, partially withdrawing it, and again driving it in, repeating the 

 process as many as 50 times, but the abdomen did not become distended to the 

 same extent as it does when the fly feeds on a human being. A large amount of 

 effort seemed to be necessary in retracting the proboscis, the forelegs being pushed 

 hard against the surface of the liver. 



At 5 p.m., six flies were dead, and I saw several flies feeding on these dead ones, 

 the ventral surface of the abdomen being chosen as the site for the insertion of 

 the proboscis, the dead fly lying on its back. 



Later in the evening, I saw a larva deposited on the twig in the bottle. The 

 larva was born tail-first, i.e., the tumid lips preceding the head and being 

 deposited on to the twig, the rest of the body remaining at right angles to it ; 

 but later the larva assumed a more vertical position. This larva never showed 

 any movement, and I am inclined to think that it was killed by the last segment 

 coming into such close contact with the twig. About an hour later, I noticed 

 that four larvae had been deposited on the floor of the bottle. 



