. An introduction to zoology, with directions for practical work (invertebrates). Fig. 212.âAphis off Sycamore. (Winged form.) food supply. When this is running short, owing to the large number of wingless individuals produced, then winged forms appear, which ' migrate to a fresh plant and there found a new colony. Young are pro- duced by these winged forms also parthenogeneti- cally, and they closely resemble their parent. The wings of any winged individuals grow gradually with the successive moults of the skin. In some cases these winged individuals go though their gradual development protec
. An introduction to zoology, with directions for practical work (invertebrates). Fig. 212.âAphis off Sycamore. (Winged form.) food supply. When this is running short, owing to the large number of wingless individuals produced, then winged forms appear, which ' migrate to a fresh plant and there found a new colony. Young are pro- duced by these winged forms also parthenogeneti- cally, and they closely resemble their parent. The wings of any winged individuals grow gradually with the successive moults of the skin. In some cases these winged individuals go though their gradual development protected by a delicate web of silk threads stretched across part of the leaf. In the autumn, however, there always appear normally sexual individuals. The females are always wingless, and usually smaller than the members of the previous summer broods. The males are usually winged, though wingless males do occur. The fertilised eggs are laid amongst the scales of tlie buds of the plant on which the Aphis feeds, and ^^0 ^^ these eggs are able to en- dure the cold of winter which kills the adult insects. They hatch in the spring, and so start the race afresh. Sometimes in ^lo- 213. ^ .? the autumn », a dead Aplils that has been attacked by the Parasite. ' - â â¢â - under syca- more, lime, or fern leaves, the dead outer skin of a winged Aphis may be found fixed on to a light-brown disc formed of interwoven silken threads (see Fig. 213, V). Within this disc may be seen moving a little legless grub. hymenopterous parasite Protm, one of the false Ichneumon-flies ; &, disc woven of silk threads concealing the larva of Praon which has now left the body of the Aphis. Lower on the leaf a disc is shown in sur- face 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 Lulham, Rosalie Blanche Jermaine. London, Ma
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