. Entomology : with special reference to its biological and economic aspects. and the^urrounding planttissue^ is stimulated to grovv^ rapidlyand abnormally into a ^all, whichserves as food for the larva; thistransforms within the gall and es-capes as a winged insect. Thephysiology of gall-formation is farfrornBeiiigunderstood. It has beenfoimdfhlifTh~e mechanical irritation from the ovipositor is notthe initial stimulus to the development of a gall; neither isthe fluid which is injected by the female during being probaHy a lubricant; if the egg is removed, the galldoes no
. Entomology : with special reference to its biological and economic aspects. and the^urrounding planttissue^ is stimulated to grovv^ rapidlyand abnormally into a ^all, whichserves as food for the larva; thistransforms within the gall and es-capes as a winged insect. Thephysiology of gall-formation is farfrornBeiiigunderstood. It has beenfoimdfhlifTh~e mechanical irritation from the ovipositor is notthe initial stimulus to the development of a gall; neither isthe fluid which is injected by the female during being probaHy a lubricant; if the egg is removed, the galldoes not appear. Ordinarily the gall does not begin to growuntil the egg has hatched, and then the gaJL^rows along withthe larvaf exceptions to this are found in some Hymenopterain which the egg itself increases in \()lume, when the gall maygrow with the egg. It appears that the larva exudes somefluid which acts upon the protoplasm of certain plant cells (thecambium and other cells capable of further growth and multi-plication) in such a way as to stimulate their increase in size. Cockscomb gall of Coloplui uh>iicola,on elm. Sliafhtlv reduced. 256 ENTOMOLOGY and number. \Miy the gall should have a distinctive^ or spe-cTEcTform. it is not yet known. There is no evidence that theform is of any adaptive importance, and the subject probablyadmits of a purely mechanical explanation — a problem for thefuture. Gall Insects. •— The study of gall insects is in many r_esp£Ctsdi„fficult. It is not at all certain ^hat an insectjvvhictuemergesfrom a gall is the species that made it; for many species, evenof Cynipidse, make no galls theniselyes but lay their eggs ingalls made by other species. Such guest-insects are termedinquilmes. Furthermore, both gall-makers and inquilines areattacked by :iiienopter:a, making the interrelationsof these insects hardJxL_deLer:mine. ]\Iany specks of insectsfeed upon the substance of ^alls; thus Sharp speaks of asmany^sTTiirty dififerent ki
Size: 1195px × 2091px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1900, booksubjectentomology, bookyear1
