f>02 THE MICROSCOPE. 



which are of a harder consistence than the rest of the 

 foody, out of its case ; and as the latter is but little, if at 

 all, heavier than the water, the creature easily drags it 

 along behind, thus keeping its abdomen always sheltered. 

 It adheres stoutly to the inside of its dwelling by means of 

 a pair of articulated caudal appendages, generally assisted 

 by three tubercles on the first abdominal segment. Before 

 changing to the pupa state, the larva fixes his case to some 

 object in the water, and then closes up the two extremities 

 with a silken grating, through which the water necessary 

 for the respiration of the pupa readily passes. The pupa 

 is furnished with a large pair of hooked jaws, by means of 

 which, when about to assume the perfect state, it bites 

 through the grating of its prison, and thus sets itself free 

 in the water. In this form the pupae of some species 

 swim freely through the water by means of their long hind 

 legs, or creep about plants with the other four ; frequently 

 rising to the surface of the water, they there undergo their 

 final change, using their deserted skin as a sort of raft, 

 from which to rise into the air ; others climb to the surface 

 of aquatic plants for the same purpose. 



The perfect insect (Phryganea grandis) has four wings, 

 with branched nervures, the anterior pair of which, clothed 

 with hairs, are more frequently used than the posterior. 

 The organs of the mouth, except the palpi, are rudimen- 

 tary, and apparently quite unfit for use. The head is fur- 

 nished with a pair of large eyes, and with three ocelli ; 

 the antennae are generally very long. Some species are so 

 exactly like Moths, that they have often been supposed to 

 belong to the Lepidopterous order ; in point of fact, these 

 insects may be considered to form a connecting link 

 between the Neuroptera and the Lepidoptera. The females 

 have been seen to descend to the depth of a foot or more 

 in the water, to deposit their eggs. 



Eggs of Insects, Plate VI. No. 124, &c. — In form, 

 colour, and variety of design, the eggs of insects are more 

 surprisingly varied than those of the feathered tribes ; 

 hut as from their smallness they escape observation, our 

 acquaintance with their structure and peculiarities is neces- 

 sarily limited and imperfect. Although the eggs of the 

 animal series differ much in their external characteristics, 



