THE SAW-FLIES. 397 



CADDIS-FLIES; TRICHOPTERA. 



QUITTING the Neuroptera, we must give a few lines to another order of insects, the 

 TRICHOPTEEA, popularly known by the name of CADDIS-FLIES. 



These insects, of which there are many species, are chiefly remarkable in their larval state, 

 on account of the curious portable habitations which they construct. All anglers are familial 

 with the Caddis, and the singular variety of form and material employed in the construction 

 of its home. Being a soft, white grub, totally unarmed, and presenting a most delicate morsel 

 to every river-fish, the Caddis is forced to conceal itself in some way from its innumerable foes. 

 For this purpose, it builds around itself a nearly cylindrical tube, open at each end, and com- 

 posed of substances varying according to the locality and the species. Sometimes these tubes 

 are made wholly of short pieces of stick, laid sometimes side by side, and sometimes in a 

 partly spiral form, something like the wires of the submarine telegraph. Sometimes the tubes 

 are made of sand or little stones, while the deserted shells of the planorbis, and other fresh- 

 water shells, are very common materials. 



FLIES AND BEES; H YMENOPTER A. 



WE now come to a vast order of insects, technically called the HYMENOPTERA. In these 

 insects the wings are four in number, transparent, membranous, the veins comparatively few, 

 and the hinder pair smaller than the others. Their mouth is furnished with powerful horny 

 jaws, and with a tongue guarded by the modified maxillae. The females are armed with a 

 many-valved sting or ovipositor. In this enormous order are included all the bees, wasps, and 

 their kin, the great family of saw-flies, the ichneumons, the gall-flies, and the ants, each 

 single family being so large, and presenting so many points of interest, that an entire volume 

 could be devoted to them with great profit. Our space, however, prohibits us from attempting 

 more than a slight sketch of each family, together with descriptions of a few typical species. 

 Without, therefore, enumerating the various arrangements of this large order, or the charac- 

 teristics on which they are founded, we will proceed at once to the family of the Tenthredinidse, 

 or Saw-flies, the first in Mr. Westwood's system. 



In this and the next family, the females are furnished with a peculiar ovipositor, com- 

 posed of several pieces, and which, though connected with a gland secreting an irritant fluid, 

 are not envenomed as in the bees, wasps, and their kin. All these insects are comprised under 

 the general term of Terebrantia, or borers, and fall easily into two large groups, in one of 

 which the abdomen proceeds directly from the thorax, and in the other is connected with the 

 thorax by means of a footstalk. Each of these groups is further subdivided, as will be seen 

 in the course of the following pages. 



The true Saw-flies are known by the curious piece of animal mechanism from which they 

 derive their name. The females of this family are supplied with a pair of horny saws, placed 

 side by side on the lower extremity of the abdomen. 



These saws are of various forms, according to the particular species to which they belong, 

 and may be seen even in the dried specimens, the top of their sheath slightly projecting, and 

 their shapes plainly visible after the removal of a portion of the abdomen. When taken from 

 the insect and placed under the microscope, they present a very pretty appearance, owing 

 to the gently-curved ribs with which their sides are strengthened and decorated. The saws 

 act alternately, one being pushed forward as the other is being retracted. Their object is 

 to form a groove in some plant, in which the eggs of the mother insect can be deposited, 

 and wherein they shall find a supply of nourishment in order to enable them to complete their 

 development ; for it is a most remarkable fact that, after the egg is deposited in the groove, 

 it rapidly increases in size, obtaining twice its former dimensions. 



