Economic entomology for the farmer and the fruit grower, and for use as a text-book in agricultural schools and colleges; economicentomolo00smit Year: 1906 Tracheal tube, showing the structure and methods of l)ranching. Fig. 18. Spiracles and their protection.—a, plate-like covering ol white grubs, cross-sec tioned at b, to show how air enters; c, a toothed slit; d, spiracle set on a teat-like process; e, conical spiracle set in a pit, protected by crossed hairs as shown sX f in section ; g, lip-like spiracle ; h and ;', unprotected round or slit-like openings. Fic;. 19. Fig. 20.

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