INSECTA. 137 



partly as varnish, is found encrusted on the small branches 

 of trees. In the natural state, this production is termed 

 stock lac ; separated from the rougher particles, it is 

 seed lac ; these particles collected, melted, and formed 

 into cakes, is lump-lac, and, when again transformed, by 

 further preparation, is found in thin, transparent scales, 

 called shell-lac, the value of which depends on its greater 

 or lesser transparency. The crust of gum-lac found on 

 the branches is half a line in thickness, and in every cell 

 measuring two lines in length, is found entombed the 

 crimson-hued insect, separated from which, the lac is as 

 yellow as amber. Whether this lac is the overflowing 

 of sap caused by the punctures of the coccus, or a secre- 

 tion exuded by their own bodies, is not decided. A cer- 

 tain tree in China, producing a kind of wax from which 

 tapers are manufactured, is the home of a particular spe- 

 cies of coccos which causes this singular exudation. 



We now close the description of this remarkable order, 

 and proceed to describe some of the most important of the 



TRANSPARENT- WINGED INSECTS. 



These families are divided into two families : the 

 Aquatic and Terrestrial. To the latter belong 



The LibettulfB (dragon-flies or adder- bolts), distin- 

 guished by their slender bodies and gauze-like wings, 

 which are often beautifully colored and composed of a 

 tracery of the finest net-work. These brilliant insects 

 may be always seen in the neighborhood of pools and 

 brooks, flying with the rapidity of lightning, their bright 

 colors glancing in the sunlight, in pursuit of all other 

 insects, as, being extremely voracious, they are unspar- 

 ing of their victims. Their teeth and mandibles are 



