90 ENTOMOLOGICAL SOCIETY 



The lack of means of aerial existence and of locomotion on land 

 has kept the fish from terrestrial conquests, but aquatic insects 

 are not thus restricted, and thousands of species, including mem 

 bers of many different orders, are still able to make the ancestral 

 substitution of a terrestrial for an aquatic habitat. Many also 

 remain in the water as adults, and use their wings for swimming. 

 Some of the May-flies descend into the water to lay their eggs, 

 and in the genus Pteronarcys the adult winged insect has external 

 gills. The most conspicuous suggestion for the formation of 

 wings from gills is, perhaps, to be found in the larvae of the May 

 flies, where the gills have become subdorsal and the tracheae 

 which, in other groups, hang in brush-like clusters, are spread 

 out instead as veins of delicate, leaf-like membranes, and even ar 

 ranged in a manner strongly suggestive of the patterns of the wings 

 of some adult insects of other groups. The utilization of the 

 anterior pairs of such lamillar gills as swimming organs, and their 

 subsequent further specialization as wings, is thus a supposition 

 requiring no abrupt or improbable change of structure or function, 

 and affords a rational explanation of organs otherwise as mysteri 

 ous morphologically as the wings of angels. 



So much for the argument afforded by the winged and wingless 

 earwigs, and the similarity of the jointed stylets of the earwig 

 larvas to those of Projapyx and Campodea. Shortly after writing 

 this sketch of phylogenetic possibilities, I received from Dr. 

 Filippo Silvestri,* of Bevagna, Italy, a paper in which my 

 meagre account of the anatomy of the African Projapyx is greatly 

 extended by observations on a South American species. Dr. 

 Silvestri not only agrees with me that Projapyx is the most prim 

 itive of insects, but he holds in addition that it proves the descent 

 of the insects from the diplopods, because he finds that the jointed 

 stylets are spinning organs homologous with those of Scolopen- 

 drclla and with those of the diplopod orders Crelochetat and 

 Monocheta. But if Projapyx is the larva of Japyx instead of a 

 mature insect, Dr. Silvestri's reasoning must be reversed, and 

 we should prepare ourselves to believe that the Symphyla, Dip- 

 lopoda and Pauropoda do not represent the ancestors of the hex- 



tion through a small arc, like the insects. The distances traversed are 

 too great, and the rate of speed too slow and too uniform to be explained 

 by the momentum with which the fish leaves the water. This conclusion 

 is the result of many excellent opportunities of observation within the last 

 ten years, principally in the Cape Verde region of the Atlantic. The ob 

 jection of some ichthyologists that the flying fish is not so constructed as 

 to be able to vibrate its fins in the air would also render these organs use 

 less in the water. 



* Boll. Mus. Zool. Anat. Comp. Univ. Torino, No. 399, Sept. 12, 1901. 



t Brandtia, p. 41, 1896. 



