. An introduction to zoology, with directions for practical work (invertebrates). INSECTA: LEPIDOPTERA 221 pigment is generally darker in the summer butterflies than in those which emerge in May. On the under side of their wings the two sexes are much more alike. In both there are two dark spots on the front wings, and their tips are yellow, whilst the hind wings are entirely yellow, and are covered with minute scattered black specks, with an inconspicuous black smudge at the centre of the front margin. „. The colov/ring of the wing is due to pigment, or Structme. —''^ ^^^ "^^^ °^ ^^'^^ o
. An introduction to zoology, with directions for practical work (invertebrates). INSECTA: LEPIDOPTERA 221 pigment is generally darker in the summer butterflies than in those which emerge in May. On the under side of their wings the two sexes are much more alike. In both there are two dark spots on the front wings, and their tips are yellow, whilst the hind wings are entirely yellow, and are covered with minute scattered black specks, with an inconspicuous black smudge at the centre of the front margin. „. The colov/ring of the wing is due to pigment, or Structme. —''^ ^^^ "^^^ °^ ^^'^^ other butterflies—to the striation of many thousands of little scales, which cover its surface and come off on the finger as a fine dust, if the wing is gently rubbed. Under the microscope these scales are seen to vary considerably in form, size, and tint. They are modifica- tions of hairs, and transitional stages may be seen (see Fig. 150). In their natural position on the wing, they overlap in regular series like -, ,,. ° Fig. -Scales nibbed from the wing of Pieris brassicae. the tiles on a roof, each being fixed by a short stalk into a socket in the membrane of the wing. If the scales are gently brushed ofij the characteristically few " veins " or " nervures'' of the wings will be seen, running from the base of the wing to its outer margin; these branch so frequently that the veins are far more numerous at the margin than at the base. The cross nervures in the wings of butterflies are few or are entirely absent, and so there are very few areas closed on all sides by them. Such areas are called " cells," and in the Large White Butterfly there is only one "; In some butterflies, Vanessa, there is no "cell" at all in the wing. The loing itself is formed of two delicate membranes held apart by an irregular tissue. At intervals along definite lines,. Please note that these images are extracted from scanned page
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Keywords: ., bookcentury1900, bookdecade1910, bookpublisherlondo, bookyear1913
