INNOXIOUS INSECTS FREQUENTING THE ORANGE. 195 



also of minute fuugi or their spores, which germinate on leaves and 

 bark infested with insects. 



The eggs are pearly-white and are laid in hollows upon orange leaves, 

 in clusters of ten or twelve, tightly covered with a shield of black ex- 

 cremeutitious matter. Over this is stretched a light canopy of web, in 

 which are entangled a few minute black grains of excrement. The ex- 

 treme transparency of the egg envelopes as well as of the animal itself 

 affords an unusually favorable opportunity for the study of the changes 

 that precede its birth. 



Just before hatching the embryos lie with their backs to the surface 

 of the leaf and are not curled in the egg, but the head only is bent over 

 upon the breast. As the egg-shell is absolutely transparent and the 

 embryo very nearly equally so, all internal changes of form can be 

 plainly seen. 



In hatching, the first movement seen is the formation of air bubbles, 

 which pass in rapid succession between the mouth organs aud collect 

 in a larger bubble within the head of the embryo. From time to time 

 this larger bubble passes through the constriction of the neck and dis- 

 appears in the body cavity. The head of the embryo gradually swells, 

 elongates, and distends the elastic egg-shell at the end, until this finally 

 bursts and the young insect protrudes its body, curving upwards and 

 forwards. 



Air continues to pass through the neck into the abdomen, which be- 

 comes greatly distended and elongated, showing the segments. A mus- 

 cular movement not connected with the passage of the air bubbles is 

 seen in the frontal part of the head and the occiput is frequently drawn 

 inwards, forming a deep depression. 



The bursting of the first larval skin was not witnessed, but it evidently 

 takes place soon after the abdomen is fully distended. The larva re- 

 mains for many hours in an erect position, with the tip of the body 

 clasped by the egg-shell and the cast larval skin. The head, at first 

 elongate, becomes transverse and there is a general contraction and 

 change of form in all the parts. 



After the larva has freed itself from the ^egg-shell and envelopes, the 

 abdomen is gradually contracted by the exertion of considerable and 

 long-continued muscular effort and changes from a cylindrical to a cor- 

 date form. 



The process of hatching occupies several days, and the young, as we 

 have seen, make their entrance into the world, like a marsupial, in a 

 somewhat rudimentary condition. 



The Orange Psocus lives chiefly upon the leaves of plants, associated 

 in small flocks or families. It passes the greater part of its life hiding 

 under the canopies of web erected over the egg-clusters. Here the 

 mother awaits the appearance of her brood, and here the young insects 

 cluster, sallying forth from time to time with the adult in search of 

 food. 



