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Some of these have the same type of sucking mouth-parts and have habits very similar to the house-fly, but as they are usually much less common and as nearly all that has been said in regard to the house-fly would apply equally well to them and as the same measures should be adopted in fighting them they need not be discussed further here.
It is the mouth that acts as the barrow. A tiny ball of earth is held between the fangs and is supported by the palpi, or feelers, which are little arms employed in the service of the mouth-parts. The Lycosa descends cautiously from her turret, goes to some distance to get rid of her burden and quickly dives down again to bring up more.
Then the skin splits across the head and down the thorax. The tattered slough is thrust back; and the pseudochrysalis appears in sight, absolutely naked. It is white at first, as the larva was; but by degrees and fairly rapidly it turns to the russet hue of virgin wax, with a brighter red at the tips of the various tubercles which indicate the future legs and mouth-parts.
Powerful curved mandibles, with two or three little teeth at the end, of a fairly bright red. Labial palpi rather bulky, short and with three joints, like the antennæ. The mouth-parts, labrum, mandibles and palpi are movable and stir slightly, as though seeking food. A small brown speck near the base of each antenna, marking the place of the future eyes.
In his remarks "On the Origin of Insects," Sir John Lubbock says, "I feel great difficulty in conceiving by what natural process an insect with a suctorial mouth like that of a gnat or butterfly could be developed from a powerfully mandibulate type like the Orthoptera, or even from the Neuroptera." Is it not more difficult to account for the origin of the mouth-parts at all?
The head is in form much like that of certain larvæ of Neuroptera and of Forficula, an Orthopterous insect. The antennæ are usually four-jointed, and vary in length in the different genera. The mouth-parts are very difficult to make out, but by soaking the insect in potash for twenty-four hours, thus rendering the body transparent, they can be satisfactorily observed.
This is seen especially in the mouth-parts which are withdrawn into the head, and become very rudimentary, affording a gradual passage into the mouth-parts of the Poduridæ, which we now describe.
When this is fully extended it is somewhat longer than the head; when not distended and in use it is doubled back in the cavity on the under side of the head. These are covered with many fine corrugated ridges, which under the microscope look like fine spirals and are known as pseudotracheæ. Thus it will be seen that the house-fly's mouth-parts are fitted for sucking and not for biting.
Another puzzle for the evolutionist to solve is how to account for the change from the caterpillar with its powerful jaws, to the butterfly with its sucking or haustellate mouth-parts. We shall best approach the solution of this difficult problem by a study of a wide range of facts, but a few of which can be here noticed.
The effect is instantaneous: total inertia, except of the appendages of the head, the antennae and mouth-parts. I achieved the same results, the same prick at a definite, invariable point, with my several operators, renewed from time to time by some lucky cast of the net.
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