. E PREGIUDIZIEVOLE insetti utili; introduzione allo studio di entomologia economica. Insetti; insetti utili; pesti di insetto. ali sono molto simili nelle prime due ma il verde venata di specie ha venature verdastre sul lato inferiore delle zampe posteriori ali. Le larve possono essere distinti senza troppa difficoltà. Quella dei grandi specie è giallo, macchiato con nero; che del piccolo cavolo bianco è di colore verde, macchiato di nero e giallo; mentre la larva del verde-specie venato è verde in tutto, eccetto per il colore rossastro spiracles, e un bordo giallo che circonda ciascuno. Le uova del

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. Injurious and useful insects; an introduction to the study of economic entomology. Insects; Beneficial insects; Insect pests. wings are very similar in the first two, but the green-veined species has greenish veins on the under side of the hind wings. The larvae can be distinguished without much difficulty. That of the large species is yellow, spotted with black; that of the small cabbage white is green, spotted with black and yellow; while the larva of the green-veined species is green all over, except for the reddish spiracles, and a yellow border which surrounds each one. The eggs of the first species are laid in clusters on the under side of a leaf, while those of the other two are laid singly. Wintering as pupse, the insects emerge in spring as butteriiies, and com- monly produce two broods in the course of the sum- mer. There is, therefore, no time between April and October when we may not see the butterflies flitting over the fields, while the larvse often feed till near Christmas. When full-fed they quit the food-plant, and betake themselves to the nearest dry and shel- tered refuge that they can find. There they proceed to hang themselves up and pupate. The larva creeps up a paling or wall, chooses a convenient spot, and covers it with a little hillock of silk, to which the tail-end of the body, which bears hooks, is soon attached. But since the pupae of the cabbage whites do not hang downwards, like many other Lepidopterous pupae, but rest upright, a second attachment is provided. This takes the form of a girdle. Silken threads, issuing from the mouth of the larva, are passed backwards and forwards from one point of the supporting surface to another, and attached at both ends. When enough threads have been spun to give due strength to the girdle, the larval skin. Fig. 45.—Small cabbage white. The upper figure represents the female.. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readabilit

Parole chiave associate all'immagine

• bookcentury1900
• bookdecade1900
• booksubjectinsects
• bookyear1902