Entomology : with special reference to its biological and economic aspects . \vhile the imaginal organsare continuing their development. Phagocytes.—The destruc-tion of larval tissues, or his-tolysis, is due often to theamoeboid blood corpuscles,known as leucocytes or phago-cytes, which attack some tis-sues and absorb their mate-rial, but later are themselvesfood for the developing imagi-nal tissues. The constructionof tissues is termed histo-genesis. In Coleoptera, however, thedegeneration of the larval mus-cles is entirely chemical, therebeing no evidence of phago-cytosis, according to Dr. R
Entomology : with special reference to its biological and economic aspects . \vhile the imaginal organsare continuing their development. Phagocytes.—The destruc-tion of larval tissues, or his-tolysis, is due often to theamoeboid blood corpuscles,known as leucocytes or phago-cytes, which attack some tis-sues and absorb their mate-rial, but later are themselvesfood for the developing imagi-nal tissues. The constructionof tissues is termed histo-genesis. In Coleoptera, however, thedegeneration of the larval mus-cles is entirely chemical, therebeing no evidence of phago-cytosis, according to Dr. R. Berlese, indeed, goesso far as to deny in generalthe destructive action of leuco-cytes on larval tissues. Imaginal Buds.—The wingsand legs of a fly originate inthe larva in the form of cellu-lar masses, or iinaginal buds,as Weismann discovered. Thusin the larva of Corethra, thereare in each thoracic segment a pair of dorsal buds and a pairof ventral buds (Fig. 219), each bud being clearly an evagi-nation of the hypodermis at the bottom of a previous invagi-. Imaginal buds of full grown larvaof Picris, dorsal aspect, b, brain;m, mid intestine; s^, prothoracicspiracle; S*-, first abdominal spiracle;sg, silk gland; I, prothoracic bud;II, bud of fore wing; III, bud ofhind wing.—After Gonin. DEVELOPMENT I8l nation. The six ventral buds form the legs eventually; ofthe dorsal buds, the middle and posterior pairs form, respec-tively, the wings and the halteres, and the anterior pair formthe pupal respiratory processes. Each imaginal bud is situ-ated in a pcripodal cavity, the wall of which {pcripodal incin-brane) is continuous with the general hypodermis; as the legsand wings develop, they emerge from their pcripodal sacs andbecome free. In Corcthra but little histolysis occurs, most of the larvalstructures passing directly into the corresponding- structuresof the adult. Corcthra, indeed, is in many respects interme-diate between heterometabolous and holometabolous ins
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectentomology, bookyear1
