. A manual for the study of insects. Insects. LEFIDOPTERA. 201 In the flight of insects it is important that the two wings of each side should act together, and we find that this is secured in most orders by uniting them in some way. In the Lepidoptera two dis- tinct metliods are employed ; in some it is done by means of 2ijugwii^ in others by means of a p'emilui?! or its substitute. As neither the jugum nor the frenulum could be derived from the other, we infer that the primitive Lepidoptera possessed neither of these organs, but had wings that were quite distinct from each other. In the cour
. A manual for the study of insects. Insects. LEFIDOPTERA. 201 In the flight of insects it is important that the two wings of each side should act together, and we find that this is secured in most orders by uniting them in some way. In the Lepidoptera two dis- tinct metliods are employed ; in some it is done by means of 2ijugwii^ in others by means of a p'emilui?! or its substitute. As neither the jugum nor the frenulum could be derived from the other, we infer that the primitive Lepidoptera possessed neither of these organs, but had wings that were quite distinct from each other. In the course of time there was developed in some of the descendants of these primi- tive forms a jugum ; while in others there was developed a frenulum. Of course in each case the development was a gradual one, extending through many generations. Thus the frenulum at first was probably merely a bunch of hairs like those elsewhere on the wings; but these became stiffer and stiffer in succeeding genera- tions. The descendants of those ancient Lepidoptera in which a jugum was developed constitute the ^whoxdi^x JtcgatcB ; while the descendants of those in which a frenulum was developed con- stitute the suborder FrenatcB. We know but little of the Jugat3e, as nearly all of them have perished. There remain only two small families, the Hepialidae and the Microptery- gidae. But these families are very widely separated, and hence it is safe to assume that they are the remnants of what was in past times a large fauna. In the Frenatse, however, there exist to-day many families, each exhibiting its own methods of specialization. In some of these families the frenulum has been preserved and perfected to a greater or less extent. But in others a curious change has taken place. It is obvious that if the two wings of each side overlap to a great extent, their acting together will be assured by this fact. And this is. Fig. 241.—Wings of Ancea Please note that these images are extracted from sc
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectinsects, bookyear1895
