THE ANATOMY OF THE ADULT MOSQUITO 93 



Having now sketched the external configuration of these 

 insects, their internal organisation remains to be considered, 

 and will probably be best dealt with by taking separately 

 the various systems, digestive, respiratory and reproductive, 

 in their turn. 



The Anatomij of the Digestive System. — In the first 

 edition of this book I had perforce to rely mainly, alike for 

 facts and illustrations, on the work of previous writers. My 

 supply of fresh material for verification was very limited, 

 and hence numerous inaccuracies were reproduced. A 

 notable example of this was Arribalzaga's illustration of the 

 general relations of the digestive organs. In this figure the 

 salivary glands are shown protruding from the back of the 

 head, which, as a matter of fact, is just where they are seen 

 in the ordinary course of dissection ; as they are drawn out 

 from their natural position in the soft neck connecting the 

 head and thorax by the act of pulling away the oesophagus 

 from the thorax. He appears to have then hastily sketched 

 in an outline of the insect, and hence these glands are made 

 to appear as if placed in the anterior part of the thorax. 



The present chapter is, however, the outcome of personal 

 observation, and the illustrations, w^ith a few duly noted 

 exceptions, are reproductions of pen and ink drawings from 

 camera lucida outlines, and so may at least be trusted as to 

 the relative size and position of the parts represented. 



The digestive tube may be said to commence at the 

 extremity of the proboscis. By the alternate retraction and 

 protrusion of the labrum ; as regards its relative position to 

 the lancets, the whole of the styles of the proboscis are 

 gradually worked into the wound inflicted, slightly in 

 advance, by the mandibles and maxillae ; the hypopharynx, 

 which is a delicate, flexible tube, far too yielding to be 

 forced unsupported into any substance, lying along the 

 groove of the labrum. Imagine a surgeon's " director," 

 with a piece of thin drainage tube carried against its groove, 

 and with four slender bistouries grouped round it, and yoM 

 will have a fair working model of the malaria-inoculating 

 apparatus of the mosquito. 



From this it follows that it is only through the tube 



