40 MOSQUITOES OF NORTH AMERICA 



the salivary duct. That Menzbier is incorrect in affinning that the hypopharynx 

 has no complete tube I have clearly proved in my observations on Bombylius 

 and Eristalis; but the question still remains unsettled whether Culex has any 

 passage, either tube or groove, through the hypopharynx. Reaumur * (tome 4, 

 part 3, 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 afiirmed, 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 with- 

 drawn 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 the amount of 

 poisonous effect upon me, as proved by numerous experiments, is in direct pro- 

 portion to the length of time which the Culex has occupied in actually drawing 

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

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

 sitate 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 salivary 

 duct in other diptera, leads me to believe, without as yet being able to give 

 anatomical proof for it, that the hypopharynx of Culex contains a duct that 

 pours out its poisonous saliva. Having no fresh specimens of Culex ciliatus, and 

 the extreme minuteness of the hypopharynx in the species of Culex available, has 

 precluded my determination of the actual presence of glands in connection witli 

 this mouth-part. 



" The mandibles (figs. 1 and 8, m), the most delicate of the mouth-parts of 

 Culex are two very thin linear-lanceolate lamellae of transparent chitin, which 

 rest with their inner edges beneath each half of the hypopharynx, their outer 

 edges projecting beyond its outer edge, on each side. At the base of the proboscis 

 they appear to have no muscular attachments. They are slightly tapering from 

 the base to the tip, but are of equal thickness throughout their breadth ; at the 

 tip they have a slight thickening, in form of a letter V, with its opening turned 

 toward their very delicate, almost invisible tip. (See fig. 5, m.) 



"The maxillae (mistaken by Gerstfeldtf for the mandibles, but correctly 

 figured by Muhr $ on his diagram as maxillae) are tapering lamellae of chitin, 

 apparently serrate at the tips. Each maxilla is thicker near the inner edge, the 

 thickening being formed by a solid chitinous shaft, which is fixed longitudinally 

 upon the upper side. (See figs. 5 and 8, mx.) The bases of the maxillae join 



• Reaumur, R. A. F. M6molres pour servir a I'hlstoire des Insectes [Edition 1737- 



1748, t. 4, part 2.] 



t Gerstfeldt, G. Ueber die Mundthelle der saugenden Insecten .... 1853. 



t Muhr, J. Die Mundthelle der Insekten dargestellt auf 5 Wandtafeln. . . .1878. 



