310 THE MICROSCOPE. 



much as if a man were to take a leap a quarter of a mile high. This 

 extraordinary activity appears to be principally occasioned by the great 

 length of the thighs of the insect, which are also furnished on their 

 outer margin with a fringe of stiff hairs or strong spines, which are of 

 great use to the insect in leaping. 



The Hymenoptera are distinguished from the other insects with 

 membranous wings, by the presence of an ovipositor of peculiar con- 

 struction at the extremity of the abdomen in the females, which not 

 only serves for placing the eggs in the required position, but also in 

 many species (Bees, Wasps, &c.) constitutes a most formidable offensive 

 weapon. As the structure of this organ, which is rarely absent, is 

 essentially the same throughout the order, the form of its component 

 parts being merely modified to suit the exigences of the different 

 insects, a short description of its general construction will not be out of 

 place here. The ovipositor, or sting, generally consists of five pieces : 

 a pair of horny valves (fig. 144), which form a sheath for the true 

 sting or ovipositor j these are jointed at the point where they issue 

 from the cavity of the last abdominal segment, and the last joint is 

 usually as long as the sting itself. - The latter consists of three bristles, 

 of which the superior is channelled along its lower surface, for the 

 reception of a pair of finer bristles, which are toothed at the tip. These 

 three pieces, when fitted together, form a narrow tube, through which 

 the egg passes to its destination ; and through this also the poisonous 

 fluid, which renders the sting of the bee so painful, is injected into the 

 wound. In the saw-fly one of these parts remains rudimentary ; but 

 in other respects the organ is the same. 



The larvae of most of the Hymenoptera are footless grubs, usually 

 furnished with a soft head, exhibiting but little, if any advance upon 

 the maggots of the Diptera. In the saw-flies, however, the larva, 

 instead of being, as above described, a mere footless maggot, presents 

 the closest resemblance to the caterpillars of the Lepidoptera, being 

 provided with a distinct horny head, and not only with six thoracic 

 legs, but also, in most cases, with from twelve to sixteen pro-legs, 

 situated upon the abdominal segments. 



The Saw-fly, fig. 141, so destructive to gooseberry-bushes, is remark- 

 able for the manner in which the female provides for the safety of her 

 eggs. This fly has a flat yellow body, and four transparent wings, the 

 outer two of which are marked with brown on the edge. The female 

 lays her eggs on the under-side of the leaf, on the projecting veins ; and 

 these are so firmly attached, that they cannot be removed without 

 crushing them. The instrument which the little insect uses for the 



