Economic entomology for the farmer and fruit-grower [microform] : and for use as a text-book in agricultural schools and colleges economicentomolo00insmit Year: 1896 Tracheal tube, showing the structure and methods of branching. Fig. 18. Spiracles and their protection.—a, plate-like covering ot 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 at y in section ; g, lip-like spiracle ; h and i, unprotected round or slit-like openings. Fig. 19. Fig. 20.

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