. The American entomologist. Entomology. THE AMERICAN ENTOMOLOGIST. 261 Fig. 137.]. Mandible of Phylhcttis- tis (after Chambers). we see it accompanied by articulated legs —always so in the pupa state. There seems to be a regular ascending scale of evolution epitomized, for instance, in Lit/i- ocoUetis. The fact that the articulated legs al- ways succeed the mem- braneous ones ; that what I have called the second form of trophi always succeeds the first, and is succeeded by that of the pupa and imago, seems to indicate that the organs which characterize the later forms have been acquired later
. The American entomologist. Entomology. THE AMERICAN ENTOMOLOGIST. 261 Fig. 137.]. Mandible of Phylhcttis- tis (after Chambers). we see it accompanied by articulated legs —always so in the pupa state. There seems to be a regular ascending scale of evolution epitomized, for instance, in Lit/i- ocoUetis. The fact that the articulated legs al- ways succeed the mem- braneous ones ; that what I have called the second form of trophi always succeeds the first, and is succeeded by that of the pupa and imago, seems to indicate that the organs which characterize the later forms have been acquired later in the evo- lution of the species than those which characterize the first form. But if this be so, then the earliest form of insect must have been, if not like the larva of Phylloc- in'stis, yet much more vermiform than it is sui)posed to have been by many entomolo- [Fig. 139.] gists. By the earliest form of insect we can, on a theory of evo- lution of all organic forms from one or a few elementary ones, Labium of first form in of coursc, Only mean Litnocolietis rcotnieUa\a,i- ^ ter Chambers). SOmC Stage at which evolution was arrested or became stationary so long that the characters of that stage were impressed on all of its descendants. Whether there ever was such a stage, what caused the arrest at that stage, how long it lasted, and why there were so few such stationary stages as are indicated in the articulate sub-kingdom, are matters that we do not now inquire into. If there ever was [Fig. 140.] such original insect form, it must have pos- sessed all of the organs that are common to the insect class — its de- scendants. It must Labium of first form in have been a typical in- Leucanthiza ai'iphicarpe~ //>//<j (after Chambers). sCCt. It mUSt have pOS- sessed labrum, mandibles, maxillae, max- illary palpi, labium, labial palpi, antennas, eyes, articulated legs, and wings or their originals (branchiae ?). If so, then all lar-. Please note that these images are extra
Size: 1337px × 1869px
Photo credit: © Library Book Collection / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1880, booksubjectentomology, bookyear1
