. The elements of insect anatomy; an outline for the use of students in entomological laboratories. 87 when the more primitive or generalized members of different orders are compared with each other. In most of the orders of insects the greater number of species have become so modified or specialized as regards the structure of their wings that it is difficult at first to trace out the primitive type. NOTE.—The student should have a clear idea of the significance of the terms generalized and specialized, which are now much used in biology. Generalized indicates a primitive condition, a nearnes
. The elements of insect anatomy; an outline for the use of students in entomological laboratories. 87 when the more primitive or generalized members of different orders are compared with each other. In most of the orders of insects the greater number of species have become so modified or specialized as regards the structure of their wings that it is difficult at first to trace out the primitive type. NOTE.—The student should have a clear idea of the significance of the terms generalized and specialized, which are now much used in biology. Generalized indicates a primitive condition, a nearness to ancestral forms. Thus, the most generalized member of a group (as a family or an order) is that member which most clearly resembles the ancient progenitor of that group. Specialized, on the other hand, indicates remoteness from the primitive type, an adaptation to more special conditions of existence. Thus, the most specialized member of a group is the one that departs most widely from the ancient progenitor of that group. These terms are used in a comparative sense ; thus, a highly specialized form may be regarded as generalized when compared with forms that are still more highly specialized. The specimens indicated for the student to study in the following part of this course have been selected with care to Sc. FIG. 2.—Wing of Rhyphus. illustrate gradually increasing degrees of divergence from the primitive type. In the case of each order studied, the work begins with a comparatively generalized form, and passes step by step to those that are more specialized. The flies of the genus Rhyphus afford good examples of comparatively generalized wings. By studying a wing of one of these flies and the accompanying figure (Fig. 2) the. 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 resemble the original Comstock, John Henry,
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