The Poison-Apparatus of the Mosquito. 885 
flattened so as to form the floor of a sucking tube whose sides and 
roof are formed by the grooved labrum (or labrum-epipharynx 
according to Dimmock). This sucking tube extends back in the 
head, piercing between the upper and lower brain, and enlarged 
in the posterior part of the head into a large pumping organ, 
which forces the imbibed fluid backwards into the cesophagus 
and stomach. 
In the last century Reaumur thought he could detect a drop of 
saliva ejected by the proboscis when stinging; he supposed that 
this is poisonous, and that its special function is to prevent the 
coagulation, and thus to promote the flow of blood by suction 
when the insect operates on our skin. We do not believe that 
he possessed any instrument that could show the poison; but his 
inference as to the presence of poison and its function is almost 
certainly correct. It seems to us, however, that the chief food of 
this insect is not animal blood, but the proteids of plants; and 
probably the fluid ejected may prevent the coagulation of all pro- 
teids, and so promote the process of suction. 
It has been very often suspected that the poison-duct is con- 
tained in the hypopharynx, which has a thickened axis, like a rod, 
Supposed by some observers to be tubular. Dimmock made out 
the tubular character of the corresponding part of some of the 
larger non-poisonous Diptera, but he was not able to demonstrate 
its tubular character in Culex. In addition to his observations 
that go to prove the existence of poison in its bite, I may add 
my own observation, that even when failing to draw blood its bite 
will sometimes swell the part, the subcutaneous tissue being irri- 
tated by poisonous matter. He concludes from the careful exam- 
ination of all the parts that no other channel can conduct this 
poison ; and adds, “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 of it, that the hypo- 
pharynx of Culex contains a duct that pours out its’ poisonous 
saliva” ; and he further states that he was unable to determine the 
actual presence of the glands. 
A year ago I succeeded in making out the duct and also the 
glands, and published a preliminary note; I was unable, however, 
at that time, to correct errors or to complete the work. This 
