. Animal life as affected by the natural conditions of existence. Animal ecology. ORIGIN OF LARVA-FORMS. 127 as insects, in the well-known walking-stick insects, allies of the grasshoppers (fig. 32), which resemble a more or less dried-up twig or shoot. Many of these species are wingless, so that they bear a wonderful resemblance to the larvae of other, winged forms. If then we assume that the wingless forms are the progenitors of winged forms, the origin of the winged forms may be very well explained by the further assumption that the optimum temperature necessary for maturing the eggs may ha
. Animal life as affected by the natural conditions of existence. Animal ecology. ORIGIN OF LARVA-FORMS. 127 as insects, in the well-known walking-stick insects, allies of the grasshoppers (fig. 32), which resemble a more or less dried-up twig or shoot. Many of these species are wingless, so that they bear a wonderful resemblance to the larvae of other, winged forms. If then we assume that the wingless forms are the progenitors of winged forms, the origin of the winged forms may be very well explained by the further assumption that the optimum temperature necessary for maturing the eggs may have been raised so much as to afford more time for assiinila-. Fig. Z2.—P/tasma sp., a -wingless orthopterous insect. tion and growth, and consequently for more extensive modifica- tions of structure. If, on the other hand, we regard the wing- less species as the later form and derived from the winged species, their origin may be easily explained by assuming that the optimum of temperature for the maturing of the eggs was lowered, while the optimum for growth remained the same. For we know that in many cases, particularly among insects, the life of the individual ends as soon as the eggs are mature and deposited, and that the performance of this function seems. 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 Semper, C. (Carl), 1832-1893. New York, D. Appleton and Co.
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