BRITISH BLOODSUCKERS 255 



(like a camel's foot) on the skin of the victim. The 

 grooved and dagger-shaped organ, marked LBR, is 

 the labrum, or upper lip ; and the tube or sheath 

 formed by the shutting together of these two parts 

 encloses all the other organs. Combined, they 

 form a trunk or proboscis, not unlike that of the 

 elephant. But the elephant is not a bloodsucker ; 

 his trunk encircles no dangerous cutting weapon. 

 It is otherwise with the gadfly, which has a pair of 

 sharp knives within, for lancing the thick skin of 

 its unhappy victims. These knives are known as 

 mandibles, and are marked MD in the sketch, one 

 on either side of the labrum. They first pierce 

 the skin ; the maxillcc, marked MX, of which there 

 are also a pair, then lap up the blood from the 

 internal tissues. Finally, there is the true tongue 

 or lingua, marked L, which is the organ for tasting 

 it. As to the maxillary palps, marked MP, they do 

 not form part of the tube at all, but stand outside 

 it, and assist like hands in the work of manipulation. 

 This is how the mouth looks when fully opened 

 out for microscopic examination. But as the 

 fly uses it, it forms a closed tube, of which the 

 labium and the labrum are the two walls, enfold- 

 ing the lances or mandibles, and the lickers or 

 maxillae, as well as the tongue. Pack them all 

 away mentally, from MX to MX, within the two 

 covers, and you will then understand the nature 

 of the mechanism. Look back at Fig. B in 

 No. 9, and you will there observe that all the 

 parts in the mosquito answer to those in the 

 gadfly. The long upper sheath is the upper lip : 



