294 NATURAL HISTORY. [CH. XXII. 



gonia), cuckoo-spit insect (Aphrophora spumaria), or 

 plant-louse (aphis), composing the order Homoplera, 

 be examined, the resemblance with the perfect in- 

 sect will be found to be not less striking. 



If, again, the preparatory states of the grasshop- 

 per, cricket, locust, or praying mantis be noticed, 

 these insects will be found to possess through life 

 the same general form, the larvae being destitute, 

 and the pupa possessing merely the rudiments, of 

 wings. These insects differ from the preceding 

 groups (which are suctorial) in having the mouth 

 formed for mastication; they have, consequently, 

 been formed into a separate order named Orthop- 

 tera. The cockroach (Blatta), and the earwig 

 (Forficula), likewise undergo similar transforma- 

 tions, and have the mouth formed for mastication, 

 whence they are considered by some authors to 

 belong to the same order, although Dr. Leach, from 

 some differences in the perfect state, formed them 

 into two distinct orders, named Dermoptera and 

 Diclyoptera. 



The next variation is that exhibited by the drag- 

 onflies and the Mayflies, forming a portion of the 

 order Neuroptera. In these two groups the larva 

 and pupa are active, and resemble each other, ex- 

 cept that the latter is furnished with the rudiments 

 of wings ; but the organs of the mouth are of a very 

 different construction from those of the perfect in- 

 sect. The general resemblance, also, which these 

 insects bear in their preparatory state to the per- 

 fect fly, is much slighter than in the preceding 

 groups, although it is evident, from the activity of 

 the pupae, that they are not widely separated from 

 them in this respect. Mr. MacLeay has applied the 

 term subsemi-complete to this kind of transformation. 



In all the preceding instances we have observed 

 that the insect continues in an active state from the 

 period of its exclusion from the egg until that of its 

 death. In the following variations, however, a state 



