DIPTERA 



225 



he applied the isolated oesophageal diverticula to a scratch, he 

 obtained the characteristic irritation and redness. These oeso- 

 phageal diverticula contain gas-bubbles and bacteria or moulds. 

 The bubbles were shown by Schaudinn to contain carbon dioxide 

 by applying baryta-water to the diverticula, when a precipitate 

 was obtained. The fungi need further investigation, but they or 

 their products appear to be the real cause of the irritation, for 



when Schaudinn pressed the carbon dioxide out of the sac the signs 

 characteristic of the bite were still produced. It appears probable, 

 therefore, that the powerful abdominal contraction mentioned 

 above expels the gas, bacteria, and fungi from the oesophageal 

 diverticula and the saliva from the salivary glands. 



It is possible that the chemical products of the fungi, by causing 

 local irritation, bring more blood into the particular area of skin 



Fig. 25. — The Alimentary Canal of Anopheles maculipennis 

 Meigen. 



(After Nuttall and Shipley, Journal of Hygiene.) 



I, Mouth and buccal cavity; 2, pharynx; 3, oesophagus; 4, dorsal and 

 ventral oesophageal diverticula; 5, proventriculus ; 6, salivary glands ; 7, narrow 

 portion of ventriculus; 8, so-called stomach; 9, malpighian tubules; 10, intes- 

 tine; II, rectum; 12, anus. 



affected, and thus enable the mosquito to get her supply quickly, 

 for feeding only takes two to three minutes, during which time some 

 mosquitoes will so overfill themselves with blood that it may be 

 ejected per anum. The use of the carbonic acid is probably to 

 prevent the coagulation of the blood, which is drawn up the large 

 blood-tube formed by the labrum epipharynx and hypopharynx 

 by the suctorial action of the pump-like pharynx. 



Fig. 23. — Anterior End of 

 A Mandible. 



(After Nuttall and Shipley, 

 Journal of Hygiene.) 



Fig. 24.— Anterior End of 

 A Maxilla. 



(x\fter 'Nuttall and Shipley, 

 Journal of Hygiene.) 



