XVII HUNTING DIPTERA 239 



of their ceiling became too much heated, and they 

 were forced to move a little way. 



One day — ping ! ping ! the tense silk was re- 

 sounding like the parchment of a drum. Perhaps 

 an acorn has fallen on my umbrella. Soon after, 

 close together, came ping ! ping ! Has some idle 

 jester come to disturb my solitude, and fling acorns 

 or little pebbles on my umbrella ? I came out of 

 my tent and inspected the neighbourhood. Nothing ! 

 The blow was repeated. I looked upward, and the 

 mystery was explained. The Bembecids of the 

 neighbourhood, which prey on gadflies, had found 

 out the rich store of food which was keeping me 

 company, and were darting audaciously under my 

 shelter to seize the gadflies on the ceiling. Nothing 

 could have been better. I had only to keep quiet 

 and observe. 



Every moment a Bembex entered like a sudden 

 flash, and darted up to the silken ceiling, which re- 

 sounded with a dull thud. A tumult went on aloft, 

 in which one could not distinguish attacker from 

 attacked, so lively was the mel^e. The struggle was 

 very brief ; almost at once the Hymenopteron retired 

 with a captive between its feet. The dull band of 

 gadflies drew a little back all round on this sudden 

 irruption, which decimated them, but without leaving 

 the treacherous shelter. It was so hot outside ; 

 wherefore move? Plainly, such swift attack and 

 prompt departure with the prey does not allow the 

 Bembex to use a poignard according to rules. The 

 sting no doubt fulfils its of^ce, but is directed with 

 no precision towards such spots as are exposed by 

 the chances of the combat. To slay outright the 



