MATERIALS FOR A FAUNA CANADENSIS. 449 



podous insecta, having the lower appendages developed on three arti- 

 culations only, and the upper, assuming the form of wings, if at all, 

 on two articulations only. The Apterous examples will probably ap- 

 pear more certainly the more their structure is understood to be 

 degraded forms of some of the other divisions. It is at least certain 

 that the different groups of Apterous insects differ more from each 

 other than they do from some of what are considered as higher forms, 

 whilst there are various special instances of the absence of wings in 

 species obviously allied to others which are furnished with them ; so 

 that on the whole, the distinction of winged and wingless insects is of 

 little value, and the Apterous orders commonly received might pro- 

 bably be appended to others of which they are but less developed 

 examples. The degree of importance really belonging to some other 

 of the characters relied upon in classifying insects, is very doubtful. 

 One much employed is the mandibulate or suctorial character of the 

 oral apparatus, yet it has been proved that the same elements occur 

 in both structures, and the transitions from one to the other are most 

 remarkable. "We cannot think that either the abortive hind wings of 

 the Diptera, or their more completely suctorial mouth, should prevent 

 the recognition of their close affinity with Hymenoptera, and we in- 

 cline to the opinion that these two orders, the most peculiarly typical 

 of all insects, would, combined together, occupy a central position in a 

 natural distribution, around which the other leading forms might be 

 placed in the order of their tendencies of development : 1 . Neurop- 

 tera ; 2. Lepidoptera ; 3. Coleoptera ; 4. Ortlioptera ; 5. Hemiptera. 

 Confining our attention now to the Neuroptera, it seems to us, in the 

 first place, abundantly evident that the Caddis-flies, which have been 

 elevated into a distinct order under the name of Trichoptera, only 

 exhibit a modification of the Neuropterous structure in analogy with 

 Lepidoptera. Reviewing, then, the various sections which have been 

 proposed, we are inclined to the following view of the families of 

 2^europtera. We place first Libellulida, the Dragon-flies, as exhibit- 

 ing the greatest power and ferocity ; 2. Phryganeida, the Caddis-flies ; 

 3. Termitida, the White Ants, distinguished by their social habits and 

 their large consumption of food, obtained without violence ; 4. Panor. 

 pida, the Planipennes of authors, including several well-marked sub- 

 families ; and, 5. Epiiemerida, May-flies, in some respects having the 

 lowest organisation in the order, yet approaching the Libellulida in 

 their imperfect metamorphosis, as well as in the character of their 

 antennae. 



