. Text book of zoology. Zoology. 244 Arthropoda. single duct,* wliioli opens in a similar position to tlie vagina of the female. Each, of the vasa deferentia widens posteriorly to form a vesicula seminalis'. Special glandular appendages frequently- open into these ducts, or into their common portion. There is a more or less complicated copulatory organ, an evagination of the hody-wall through which the terminal portion of the seminal duct is continued, and capable of partial or complete retraction when not in use ; in many, it may possess hard chitinous portions, and lies hidden within the clo
. Text book of zoology. Zoology. 244 Arthropoda. single duct,* wliioli opens in a similar position to tlie vagina of the female. Each, of the vasa deferentia widens posteriorly to form a vesicula seminalis'. Special glandular appendages frequently- open into these ducts, or into their common portion. There is a more or less complicated copulatory organ, an evagination of the hody-wall through which the terminal portion of the seminal duct is continued, and capable of partial or complete retraction when not in use ; in many, it may possess hard chitinous portions, and lies hidden within the cloaca, from which it may be protruded during copulation. A fairly marked sexual dimorphism ocom-s very often in Insecta, due largely to tlie different parts played by tte male and female in repro- duction. Frequently the males possess apparatus wHcli is wanting in the females, or certain portions of the body are specially developed; for example, the large mandibles of the Stag-beetle, the huge eyes of the male Honey-bee, the well-developed antennse of the male Oock-chafers and many Butterflies, the broad front feet of male Water-beetles; such developments, if they are in any way explicable, are attributable to the struggles carried on by the males for the possession of the female (Stag-beetle); or, in the case of special prominence of sensory organs, they result from the needs of the male in seeking for the less active female, or the parts serve as organs of retention dtu-ing copula- tion (Water-beetles). More rarely some portion of the body of the female is specially developed; in the female 2 2 3 Nut-weevil {Balaninus nucum), the proboscis is longer than in the male, as it is used to gnaw thi-ough the yoimg nuts, in which the eggs are deposited. Not infrequently the sexes differ in. size, the pre- ponderence beiag usually on the side of the female; this may be Mg. 208. Females of three alHed species of ^^^ ^j j ^ ^j^^ ^ bulk of Geometria£e (1 Hiberniaprogemmana, 2 H. mi aurant
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectzoology, bookyear1896
