OF MANDIBULATA. 431 



and wings, all manifest their close affinity*. Yet, if the 

 Perlides of Latreille fall into the same group with the 

 Phryganea, such an order presents a singular discordance 

 in the external appearance of the imagines. For instance : 

 some, as Nemoura, have the corneous mandibles of the 

 Hymenoptera ; others, as Phryganea, have them scarcely 

 developed like the Lepidoptera ; some have a broad head 

 and the first segment of trunk large, others a small head, 

 setaceous antennee, and the first segment of trunk as smalt 

 as in the Hymenoptera. There are some with caudal ap- 

 pendages, others with none ; some with opaque, deflexed, 

 trichopterous wings, the upper larger than the under, others 

 with them horizontal, membranaceous and transparent, the 

 inferior exceeding in size the superior ; some with two ocelli, 

 others with three ; and perhaps no solid character can be 

 found for Lamarck's group of Phryganida, but the circum- 

 stance that while the perfect insects are Gymnopterous, and 

 vary excessively in external organization, the larvae are all 

 cylindrical with membranaceous feet, and undergo that me- 

 tamorphosis to which Linnaeus has applied the epithet 

 obtecla. But, if this be the character of an order of Man- 

 dibulaia, it is difficult to exclude from it the Tenthredina; 

 and indeed it is very singular that even the genus Cepha- 

 leia of Jurine scarcely possesses a leading character, in the 

 external organization of its perfect state, which may not be 

 found either in the Perlida or Phryganida. It conse- 



* We may hope that the learned entomologist who has revived this or- 

 der will change its name on another account, namely, that Meigen has 

 applied the word Trichoplera to designate certain Diptera. On Phryganea 

 being indicated as a distinct order by Degeer, his commentator Retz gave 

 it the name of Elinguia. But, besides the necessity which, for the sake of 

 uniformity, there is for naming the orders from some character of the 

 wings, this, the original name of the order, is even still more objectionable 

 on other accounts, as must be sufficiently obvious. 



