172 DIPTERA. 



be enumerated ; but we have said enough to show that these dewpised 

 vegetable parasites are by no means unprofitable members of the 

 animal creation. 



Equally well known, and unfortunately almost as 

 abundant as the Aphides, are 



The Blight Insects (Psylla\ the pests of our orchards 

 and the destructive causes of what is called " the blight " 

 upon our fruit trees. It would seem, indeed, that every 

 tree and shrub supports a special race of these creatures, 

 which are distinguished by entomologists by the names of 

 the plants upon which they are found. In the preparatory 

 stages of their growth, these insects are generally covered 

 with a white cottony substance, matted together with a 

 sweet and gummy secretion. 



The Lantern Flies (Fulgord) are distinguished by the 

 extraordinary conformation of their heads, which are ex- 

 panded into an enormous muzzle, nearly equalling in size 

 all the rest of the body. They have long had the repu- 

 tation of emitting a brilliant phosphorescent light ; but 

 whether they possess such a faculty or not is extremely 

 doubtful. 



ORDER DIPTERA.* 



The insects belonging to this Order possess but a 

 single pair of wings, which are always transparent, 

 veined, and without folds. The place of the hind 

 wings is occupied by a pair of slender filaments 

 called poisers ; their mouth is adapted for suction, 

 and in many species is supplied with piercing instru- 

 ments of very formidable character. 



To this Order belong 



The Gnats (Culex), known in foreign countries as 

 Mosquitoes, and universally dreaded, on account of the 

 sharpness of their envenomed bite. They are the most 

 insolent, the most insatiable, of blood-suckers. Their 

 terrible proboscis is a chef-d'oeuvre of mechanism. From a 

 long grooved and flexile sheath there issue forth long 

 slender darts, so sharp and subtle that they slip with ease 

 through our poor skins ; vainly we try, warned by the 



* 8/$, dis, twice, double ; irrepov, pteron, a wing. 



