We will begin our examination with the Gnat (Culex pipiens), of which Réaumur, in his "Mémoires pour servir à l'Histoire des Insectes," has given such a curious and complete history. "The gnat is our declared enemy," says Réaumur, in the introduction to his memoir, "and a very troublesome enemy it is. However, it is well to make its acquaintance, for if we pay a little attention we shall be forced to admire it, and even to admire the instrument with which it wounds us. Besides which, throughout the whole course of its life it offers most interesting matter of investigation to those who are curious to know the wonders of Nature. During a period in its life the observer, forgetting that it will at some time annoy him, feels the greatest interest in its life-history."
As this is the case, let us explain the history of these insects, which excite so much interest. The illustrious naturalist we have just mentioned will be our guide.
The body of the gnat is long and cylindrical. When in a state of repose one of its wings is crossed over the other. They present a charming appearance when seen through a microscope, their nervures, as well as their edges, being completely covered with scales, shaped like oblong plates and finely striated longitudinally. These scales are also found on all the segments of the body.
| Fig. 21.—Antennæ of Gnat, magnified. | Fig. 22.—Head of Gnat, magnified. |
The antennæ of the gnat, particularly those of the male, have a fine feathery appearance ([Fig. 21]).
Their eyes, covered with network, are so large that they cover nearly the whole of the head. Some have eyes of a brilliant green colour, but looked at in certain lights they appear red. [Fig. 22] shows the head of the gnat with its two eyes, its antennæ, and trunk.
The instrument which the gnat employs for puncturing the skin, and which is called the trunk ([Fig. 23]), is well worthy of our attention. That which is generally seen is only the case of those instruments which are intended to pierce our skin and suck our blood, and in which they are held, as lancets and other instruments are held in a surgeon's case. The case ([Fig. 24]) is cylindrical, covered with scales, and terminates in a small knob. Split from end to end that it may open, it contains a perfect bundle of stings. Réaumur tried to observe, by allowing himself to be stung by gnats, what took place during the attack. He forgot, in watching the operations of the insect, the slight pain caused by the wound, soliciting it as a favour, his only regret being not to obtain it when he wished.
Réaumur observed that the compound sting, which is about a line in length, enters the skin to the depth of about three-quarters of a line, and that during that time the case bends into a bow, until the two ends meet. He noticed besides, that the trunk-case of certain gnats was even more complicated than that which we have described. But we will not dwell any longer on this point.
Let us now try to give an idea of the construction and composition of this sting, which, after piercing the skin, draws our blood.
| Figs. 23 and 24.—Trunk of Gnat, magnified. | Figs. 25, 26, 27.—Lancets of the Gnat. |