Before we leave the region of the head, we have the important task to fulfil, of describing the mouth of the insect: this part is more complicated than the organs we have as yet seen, and requires, therefore, a considerable degree of our careful attention to enable us to do justice to it, and to carry in the mind a clear view of this interesting portion of an insect's structure. "If," writes Mr. Westwood, "a beetle, and a butterfly, a house-fly, or an aphis, be examined whilst feeding, a totally different apparatus will be found in each, although perfectly adapted for the mode of feeding. The beetle is employed in gnawing and tearing in pieces hard or fleshy substances: its instruments of manducation are, therefore, horny and robust. The butterfly, on the contrary, has to seek its food at the bottom of the tubes of flowers; and here in the glowing beams of the sun it revels in its existence, and sips the most delicious nectar. It is necessary for this purpose that it should be provided with a long and slender instrument; but, from the very structure of this apparatus, it is essential for its defence, that, so soon as the insect has ceased feeding, the instrument should be lodged in a place of safety. It is, therefore, rolled up in a beautiful spiral direction, and laid to rest between a pair of hairy appendages, which will defend it from injury. If we observe a common fly sipping up a drop of spilt wine, or revelling upon a morsel of sugar, it will be found that its mouth is totally unlike either of the former: it is short, thick, and fleshy, and acts as a sucker, the nutriment ascending through the canal which runs upward into the throat. The aphides and all their brethren have a mouth differently constructed, being a long and slender pointed canal, of a fleshy, or leathery substance, but furnished internally with several slender bristles, which the insect employs as lancets to wound its prey. In the flea, again, the structure is quite different."
[Illustration: _Proboscis of the Honey-Bee._]
[Illustration: _Proboscis of Carpenter-Bee_]
To the variations in the mouth of each of these insects it has been thought good to attach a distinct name. When, for example, we speak of a bee's _proboscis_,[V] we speak actually of its mouth. The mouth of the butterfly is called by most entomologists _antlia_; that of the aphis a _promuscis_; that of the flea a _rostrulum_. But the reader must not allow himself to be confused by these terms; they all are but names for modifications of the same part--the mouth. When the butterfly plunges its long tube into the flower--when the fly intoxicates itself with a drop of syrup, using its _proboscis_ to pump it up--and when the flea thrusts its _rostrulum_ into our flesh, and quaffs our life-blood as though it were nectar,--let us not forget the mouth is the organ employed in each of these cases, varied and altered in form though it certainly be.