682 FEET, STINGS, AND OVIPOSITORS OF INSECTS. 



which one disk (a) is extremely large, and is furnished wi' h strong 

 radiating fibres, a second (6) is a smaller one formed on the same 

 plan (a third, of the like kind, being often present), whilst the 

 greater number are comparatively-small tubular club-shaped bodies, 

 each having a very delicate membranous Sucker at its extremity, 

 as seen on a larger scale at b. These last seem to resemble the 

 Hairs of the Fly's foot in every particular but dimension ; and an 

 intermediate size is presented by the Hairs of many Beetles, espe- 

 cially Curculionidce. The Leg and Foot of the Dytiscus, if mounted 

 without compression, furnish a peculiarly beautiful object for the 

 Binocular Microscope. — The Feet of Caterpillars differ considerably 

 from those of perfect Insects. Those of the first three segments, 

 which are afterwards to be replaced by true-Legs, are furnished 

 with strong horny claws ; but each of those of the other segments 

 which are termed 'Pro-Legs,' is composed of a circular series of 

 comparatively-slender curved hooklets, by which the Caterpillar is 

 enabled to cling to the minute roughnesses of the surface of the 

 leaves, &c, on which it feeds. This structure is well seen in the 

 Pro-Legs of the common Silk-worm. 



531. Stings and Ovipositors. — The Insects of the Order 

 Hymenoptera are all distinguished by the prolongation of the last 

 segment of the Abdomen into a peculiar organ, which, in one divi- 

 sion of the order, is a ' Sting,' and in the other is an ' Ovipositor,' 

 — an instrument for the deposition of the eggs, which is usually 

 also provided with the means of boring a hole for their reception. 

 The former group consists of the Bees, Wasps, Ants, &c. ; the 

 latter of the Saw-flies, Gall-flies, Ichneumon -flies, &c. These two 

 sets of instruments are not so unlike in structure, as they are in 

 function. — The 'Sting' is usually formed of a pair of Darts, beset 

 with barbed teeth at their points, and furnished at their roots with 

 powerful muscles, whereby they can be caused to project from their 

 Sheath, which is a horny case formed by the prolongation of the 

 integument of the last segment, slit into two halves, which separate 

 to allow the protrusion of the sting ; whilst the peculiar ' Venom ' 

 of the sting is due to the ejection, by the same muscular action, of 

 a poisonous liquid, from a bag situated near the root of the sting, 

 which passes down a canal excavated between the darts, so as to be 

 inserted into the puncture which they make. The Stings of the 

 common Bee, Wasp, and Hornet, may all be made to display this 

 structure without much difficulty in the dissection. — The ' Oviposi- 

 tor' of such Insects as deposit their eggs in holes ready-made, or 

 in soft animal or vegetable substances (as is the case with the 

 Jchneumonidce), is simply a long tube, which is enclosed, like the 

 sting, in a cleft sheath. In the Gall-flies (Cynipidce), the extremity 

 of the Ovipositor has a toothed edge, so as to act as a kind of saw 

 whereby harder substances may be penetrated ; and thus an aperture 

 is made in the leaf, stalk, or bud of the Plant or Tree infested by 

 the particular species, in which the egg is deposited, together with 



