32 AMERICAN MUSEUM GUIDE LEAFLETS 



The Internal Organs. 



When the mosquito bites, blood is pumped up into the "sucking- 

 tube" by two pumps (Fig. 18). The first and smaller pump lies 

 just above the junction of the labrum with the head and forms a direct 



continuation with the tube. The second, larger and more 

 Pumps , n 



efficient pump, lies further back in the head and is dilated by 



powerful muscles. In section it is triangular, with collapsed walls. 



When dilated by the muscles it fills with blood from the smaller pump 



and from the tube beyond. It is then allowed to collapse by its own 



elasticity, and the liquid is forced on into the oesophagus. This is in 



great part in the neck of the insect and gives off just beyond its entrance 



into the thorax, three food reservoirs, two small ones above, and a third 



elongated sac below, which reach far into the abdomen (Fig. 26). It is 



the blood stored in this reservoir, which in its greatly distended state 



inav be seen through the thin pleural membrane, that 

 Food reservoirs . ' r . 



gives to the mosquito the red color noticeable after a 



full meal. The stomach is a continuation of the (esophagus and is 

 tubular, narrow in front but dilated into a sac behind. At its posterior 

 end is a valve-like constriction just beyond which there open into the 

 intestine five excretory tubules. After one or two rather sharp curves, 

 the intestine is continued to the terminal end of the body. 



The nervous system of the mosquito (Fig. 2(>) consists of a chain of 

 connected centers, or nerve ganglia. In the head several pairs of gan- 

 glia are fused to form the " brain," which supplies nerves to 

 Nervous . , , , T . . 



Svstem the eyes, antennae, palps and mouth-parts. In the thorax, just 



above the origin of the legs, there is another large mass con- 

 sisting of three pairs of fused ganglia which send nerves to the legs, 

 wings and balancers. The nervous system is continued in the abdomen 

 as a chain of small ganglia, six in number. In addition to this main 

 nervous system a pair of small sympathetic ganglia lie on each side of 

 the alimentary tube, in the anterior part of the thorax. 



The large thorax is almost entirely filled with the great muscles of 

 flight, consisting of two masses at right angles to each other (Fig. 26). 



Their alternate contractions change the shape of the thorax and 

 Body .... ....... ,.,, 



Muscles indirectly serve to move the wings m night. 1 lie wings are 



also controlled by smaller special wing-muscles. The muscles 



which move the abdominal segments during respiration lie for the most 



