140 NATHAN BANKS. 



the head from side to side, and keeping the palpi in motion. The 

 rail is often used to hold on to some spot, but when not in use is often 

 carried turned to one side. 



These voracious little larvae are known as "aphis-lions;" their 

 principal food being aphids. However, they will feed on almost any 

 soft insect, and even upon each other. It seizes the aphid with a 

 quick movement of the jaws and rapidly sucks the unfortunate vic- 

 tim dry, often turning it around in order to extract all the juices. 

 In this manner they destroy a great number of plant-lice in a day. 

 The innumerable hosts of aphids with their remarkable fecundity 

 are no match for the ravenous appetite of these Chrysopa larvse, and 

 in a few days plants badly infested with "green fly" are clean 

 again. Their useful habits have been commented upon by almost 

 every economic entomologist ; no* only in the destruction of plant 

 lice, but as attacking the pear-tree Psylla, scale insects, the chinch- 

 bug, elm-leaf beetle and other pests. 



The length of the larval life is from one to three weeks. AY lien 

 a proper size is reached the larva rests for a time and then proceeds 

 to spin the cocoon. This may be placed almost anywhere, sometimes 

 in a crevice of the bark or a fold in the leaf, but quite as often they 

 are fully exposed to view. The larva, which is now fusiform in 

 shape, spins around itself threads which are drawn tighter and 

 tighter till the larva is curled upon itself as closely as is possible. 

 The spinning continues and results in a practically spherical cocoon, 

 white or yellow 7 in color. Some cocoons are more elliptical than 

 others. 



The silk glands open near the end of the abdomen, and they emit 

 a single smooth thread. 



After a period of about ten days the pupa cuts off a circular lid 

 from the cocoon and crawls almost or completely out. The mandibles 

 of the pupa are short, stout and sharp-pointed, enabling the creature 

 to cut through its tough cocoon. In a few minutes its back bursts 

 along the median line and from it gradually issues the adult fly ; at 

 first pale and weak, but in the course of an hour or so assumes its 

 full coloration and development. 



Shinier has noted that in a larva that had but four legs, the adult 

 fly from it had all six legs fully developed. Since the Chrysopid 

 larva lives exposed it is not strange that they are attacked by vari- 

 ous parasites. The Chalcidids, Perilampus hyalinus, Chrysopophn- 



