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rod of chitin ; but, in C. ciliatus, a North American species of which the mouth- 

 parts are larger, this rod appeared to be tubular. Is it a rod or is it a tube? 

 Menzbier 8 writes (p. 25) that in diptera " neither the labrum nor the hypopharynx 

 possesses a completed tube, but only a channel" * which leads into the salivary 

 duct. That Menzbier is incorrect in affirming that the hypopharynx has no 

 complete tube I have clearly proved in my observations on Bomlylim and 

 Ei'istalis; but the question still remains unsettled whether Culex has any passage, 

 either tube or groove, through the hypopharynx. Reaumur 12 (tome 4, part 2, 

 p. 396) discusses the probability of a poisonous fluid being secreted by Culex, to 

 cause the blood to flow more readily when it bites, and since his time writers 

 have, on the one hand, accepted this statement, without proving the presence of 

 such a fluid or of the glands to secrete it, or they have, on the other hand, 

 denied the existence of such a fluid, and affirmed, as Leeuwenhoek did, that the 

 swelling subsequent to the bite of Culex was due to the irritation produced by 

 the tearing of the mouth-parts in the skin, without the aid of a poisonous 

 secretion. After having experimented a large number of times with the living 

 mosquito, I am convinced that there is use made of a poisonous saliva; for, 

 when biting, if the mosquito fails to strike blood, which it often does On parts 

 of the back of my hand, it may have inserted its proboscis (labium of course 

 excepted) nearly full length, in from one to six directions, in the same place 

 and withdrawn its proboscis; indeed it may have inserted its proboscis, as often 

 occurs, in extremely sensitive parts; yet in such cases, if no blood be drawn, no 

 more effect is produced upon my skin than is produced by the prick of a sharp 

 needle; a red point appears only to disappear in a few hours. Certainly there 

 has been as much tearing of tissues in such a case as the above-mentioned, as 

 there is when Culex settles on a place richer in blood, and, with a single probing, 

 draws its fill. When the insect is allowed to draw its fill on the back of my 

 hand, the subsequent swelling lasts from forty to forty-eight hours, and tha 

 amount of poisonous effect upon me, as proved by numerous experiments, is in 

 direct proportion to the length of time which the Culex has occupied in actually 

 drawing blood. The above-mentioned facts would indicate a constant outpouring 

 of some sort of poisonous fluid during the blood-sucking process, and would 

 necessitate a tube or channel for its conduction. Now no other channel exists 

 through which saliva could pass from the base to the tip in the mouth-parts which 

 Culex inserts in the skin, and this, together with the position occupied by the 



* "Dass weder das Labrum noch die Hypopharynx eine vollstiindige Rohre besitzt, 

 sondern nur einen Kanal." 



