. Annals of the Entomological Society of America. Entomology. ANNALS OF The Entomological Society of America Volume XIV JUNE, 192 1 Number 2. THE SCLERITES OF THE HEAD, AND PARTS OF CERTAIN IMMATURE ADULT INSECTS. By G. C. Crampton, Ph. D. (Massachusetts Agricultural College, Amherst, The external structures of the head, and the mouL. particular, are of considerable interest in making a study of the interrelationships and lines of descent of the different orders of insects; and it is of the greatest importance, in such a study, that we should know the correct homologies of the various parts, i
. Annals of the Entomological Society of America. Entomology. ANNALS OF The Entomological Society of America Volume XIV JUNE, 192 1 Number 2. THE SCLERITES OF THE HEAD, AND PARTS OF CERTAIN IMMATURE ADULT INSECTS. By G. C. Crampton, Ph. D. (Massachusetts Agricultural College, Amherst, The external structures of the head, and the mouL. particular, are of considerable interest in making a study of the interrelationships and lines of descent of the different orders of insects; and it is of the greatest importance, in such a study, that we should know the correct homologies of the various parts, in order to determine what paths of development have been followed in deriving the higher types of insects from the lower ones. Many investigators have made the mistake of attempting to compare the higher types directly with the lowest ones without tracing the development of these types through a series of intermediate forms, with the result that the interpretations generally accepted as correct are frequently quite the reverse, and the true meaning of the different structures has not been fully grasped in many instances. On this account, I would devote the greater part of the following discussion to the consideration of such intermediate types as the Coleoptera, Neuroptera, etc., which serve to connect the lower insects with the higher ones, since it is these inter- mediate forms alone which can furnish us with the key to the proper interpretation of the modifications of the parts met with in the higher forms. Consideration has also been given to the condition found in larval insects as well, for, although larval insects are usually modified in adaptation to their own peculiar environmental conditions, they frequently retain the head structures in a more primitive condition than their 65. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly
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