224 VENOMOUS ANIMALS : PROTOZOA TO ARTHROPODA 



During this process respiration is going on quietly, but at times, 

 according to Schaudinn, a violent contraction of the abdomen is 



noticed, which is said to 

 be due to the carbonic 

 acid in the superficial 

 layers of the skin, for he 

 found that when carbon 

 dioxide gas acted upon 

 mosquitoes a like contrac- 

 tion was produced. 



As this process is pro- 

 ceeding, an irritating sub- 

 stance, the chemical 

 nature of which is not 

 known, is injected under 

 the skin, and it is evident 

 that this happens before 

 the mosquito begins to 

 suck blood for the irrita- 

 tion is present when the 

 insect ceases to bite before drawing up the blood. 



There has been much dispute as to where this substance comes 

 from, but this appears to have been settled by Schaudinn, who 



Fig. 21 . — An Anopheline Mosquito(^ .macu- 

 lipennis Meigen) in the Act of Biting. 



(After Nuttall and Shipley, Journal of 

 Hygiene.) 



Note that the proboscis does not enter the 

 wound, and that it is bent convex posteriorly. 

 Note the distension of the abdomen as seen by 

 the space between the ter-ga and the sterna. 

 In the natural condition this space would be 

 bright red from the blood in the abdomen. 



Fig. 22. — Head of Anopheles maculipennis Meigen. 



(After Nuttall and Shipley, Journal oj Hygiene.) 



1, Labium; 2, maxillae; 3, hypopharynx; 4, mandibles; 5, labrum; 

 6, palpi; 7, antennae; 8, occiput; 9, eye; 10, clypeus. 



triturated the isolated salivary glands in salt solution, which he 

 applied to a wound with negative result. On the other hand, when 



