THE INSECT WORLD. 



371 



smoothly. We find division of labor carried to an extreme ; 

 combination for special purposes ; skill and energy in the prepa- 

 ration of homes ; and, finally, we discover the helpless young 

 cared for by parents or nurses. It is only in the Hymenoptera 

 among insects that we find true babies, — that is, young that must 

 be fed and tended until they are ready to assume the adult form. 

 Nowhere else do we find larvae fed on anything but simple, 

 natural food ; but by many bees a mixture is prepared and fed ; 

 not honey or pollen alone, but a combination of the two in defi- 

 nite proportions is given, and these proportions vary with the 

 sex of the larva. 



Members of the order Hymenoptera may always be distinguished 

 by the presence of four transparent wings, the anterior always the 

 larger, the secondaries frequently very small. They are not cov- 

 ered with scales, but are often set with small hair, and the cells 

 and veins are comparatively i^'w in number ; never netted as in the 

 Neicroptera. The mouth parts are mandibulate, or formed for 

 biting, but in many of the families there is also developed a large 

 tongue-like structure which serves for lapping, none of the Hy- 

 menoptera being strictly haustellate, or sucking insects. The 

 metamorphosis is complete. 



Taken as a whole, the order contains beneficial insects ; but as 

 there is no rule without exceptions, so we find here also one 

 series the species of which are vegetable feeders. These are in- 

 cluded in the families ToithredinidcB and UroceridcB, the "saw- 

 flies" and "horn-tails." 



The term "saw-flies" is used to indicate a series of species 

 peculiar by the structure of the ovipositor, which is made up of a 

 number of parallel blades toothed at the edge, by means of which 

 the insects are enabled to cut pockets or slits in leaves or other 

 vegetable tissues to receive the eggs. They are further peculiar 

 by having the abdomen sessile, or joined for its full width to the 

 base of the thorax, and the wings are rather larger in proportion 

 to the body than in other groups. The larvae are caterpillar-like 

 in appearance, but they always have at least one more pair of 

 prolegs than any caterpillar, — six pairs or more, of which one 

 pair is anal, — which renders them easily distinguishable. They 

 are often more or less slimy in appearance and to the touch, and 

 perhaps a majority have the habit of coiling the posterior por- 



