no HYMENOPTERA. 



with a straggling irregular motion. When full grown, the little creature creeps 

 up the stem of some aquatic plant till the mouth of its case just reaches the 

 surface of the water ; it then spins a net of silk across the entrance to its 

 abode, and goes into the pupa state. At the appointed time the pupa tears 

 its way easily throi'g'i the silken grate, crawls a few inches out of the water, 

 throws off its pupa sKin, and becomes a winged caddis-fly. 



FIG. 105. PITA-CASE, LARVA, AND FLY OF CADDIS-WOKM. 



MEMBRANE-WINGED INSECTS. ORDER HYMENOPTERA.* 



The Hymenopterous insects, like the Neuroptera, are furnished 

 with four transparent wings, but the nervures, instead of forming; 

 a very close network, are much more sparingly distributed. An- 

 other difference is that in the Hymenoptera the hind pair of wings 

 seem as if cut out of the front pair, with which, during flight, they 

 interlock by means of small hooks, so that the two wings almost 

 resemble one. The abdomen is, moreover, terminated by an 

 apparatus which in some species serves for the deposition of the 

 eggs, but in others is connected with a poison-bag, and forms a 

 venomous sting. To this Order belong 



The Saw-Flies (Tcnthredo). They derive their name from a curiously- 

 constructed instrument called an ovipositor, with which the female is pro- 

 vided. This consists of a saw composed of two blades that work alternately, 

 by means of which she makes incisions in the branches of plants, wherein she 

 deposits her eggs. The wounds thus made by the teeth of the saw frequently 

 cause the wounded part to swell into a fleshy mass resembling a fruit, in the 

 interior of which the larvae find the materials for their subsistence. The larvae 

 very much resemble caterpillars, from which, however, they are easily dis- 

 tinguished by the number of their feet : before changing into nymphs, the 

 false caterpillars enclose themselves in a cocoon, in which they remain many 

 months in their caterpillar condition, only becoming changed into nymphs a 

 few days before their final conversion into saw-flies. 



In the spring-time of the year, when the bright leaves of our gooseberry- 

 bushes first make their appearance, they are often devoured in a remarkable 

 manner, even before they have completely concealed the straggling spiny 



* i>ld)v, umen, a membrane ; irrtpov, pteron, a wing. 



