. Bulletin of the Department of Agriculture. Agriculture; Agriculture. 6 BULLETIN 808, U. S. DEPARTMENT OF AGRICULTURE. practically every wheat-growing section east of the Mississippi Elver, it rarely lias caused any serious losses in recent years, al- though it exacts a small toll annually. This possibly may be ex- plained by the fact that wheat fields in the Eastern States are lo- cated usually at a distance from the old stubble fields of the previ- ous, year, and since the spring generation is wingless, only a small percentage of the individuals is able to make the journey safely from
. Bulletin of the Department of Agriculture. Agriculture; Agriculture. 6 BULLETIN 808, U. S. DEPARTMENT OF AGRICULTURE. practically every wheat-growing section east of the Mississippi Elver, it rarely lias caused any serious losses in recent years, al- though it exacts a small toll annually. This possibly may be ex- plained by the fact that wheat fields in the Eastern States are lo- cated usually at a distance from the old stubble fields of the previ- ous, year, and since the spring generation is wingless, only a small percentage of the individuals is able to make the journey safely from one wheat field to another, and it thus becomes difficult for the species to maintain itself. H. grandis is a comparatively old offender, but probably has escaped being confused with other species, as it has some rather striking characters, though the fact that it is dimorphic greatly jDerplexed all entomologists for a number of years. Each form was considered and described as a separate and distinct species. Riley (11) described the spring form as Isosoma tritici in 1882, since he considered Fitch's tritici as a synonym of hordei Harris. In 1884 the late F. M. Webster established the dimorphic habits of grandis^ rearing both forms, and Riley (12) de- scribed the summer form as Isosoma grande. In 1896 Howard (8, p. 10) definitely established Fitch's tritici as a valid species and gave the name minutum, to the vernal generation of Riley's species previously referred to in literature as tritici. H. grandis is probably the most inter- esting species of the whole group. There is one other species that has two generations during the year, but no others, so far as is known, are. dimorphic. Fig. 3.—Wheat straw- worm : Wingless adult female of spring form (EarmoKta grandis, HOST plants. t o r m mi n ut a ). CTi*G3,tlv pulstrsTGcl __ (Webster and The Writer has never succeeded in rearing H. Reeves.) grcmdis from any plant but wheat. He has observed it oviposit in other plants but no l
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