268 MISSOURI AGRICULTURAL REPORT. 



THE SOD WEB-WORMS. 

 Crambus (several species). 



There are about sixty species of the sod web-worms in the United 

 States, only four of which are commonly found infesting corn, viz., 

 Crambus trisectns Walk., C. mutabilis Clem., both of which are two- 

 brooded, and C. luteolcllus Clem., and C. vulgivagellus Clem., both of 

 which are single-brooded. We will discuss the sod web-worms together 

 and not separately then, further than I have just given in regard to 

 broods. Outside of the variation in the number of broods among the 

 different species, their work, life history and habits are so similar that 

 it will not be necessary to discuss the separate species independently. 



These sod web-worms infest grass 

 lands of all kinds, and this is their prin- 

 cipal and normal food. They are to be 

 found every summer in considerable 

 numbers not only in the grass fields but 

 in our lawns, and the amount of damage 

 that these insects do everv 3'ear is not 



Fig. 28. — The Common Sod Web- ■" ■^ 



Worm, Crambus trisectus, Adult taken into accouut, as a rulc, simply be- 

 Moth ; enlarged about two diam- ' i j 



^^^^s- cause of the fact that we are so accus- 



tomed to a loss of upwards of ten per cent of the grass crop by the rav- 

 ages of these insects that we do not now notice them unless, as some- 

 times happens, they become unduly numerous in certain areas, in which 

 case they may ruin the entire field of grass or the lawn, so that the same 

 appears withered and dead and can be burned over when it should be 

 perfectly green and healthy. This annual loss of about ten per cent of 

 the grass would amount to many millions of dollars in the aggregate, 

 taking the entire United States over. This will give the reader some idea 

 of what is continually going on in the matter of the destruction of 

 various products by comparatively obscure insects, when the same is 

 done under what we might call normal conditions prevailing from year 

 to year. The sod web-worms do not, as a rule, injure the corn crop un- 

 less this corn follows on land which has been in sod the year previous, 

 and as a rule, for several years before turning it under in preparation 

 for the corn crop. In this case they may ruin the young corn and make 

 the second and even a third replanting necessary. 



The work of the sod web-worm in the corn is very frequently mis- 

 taken for that of the army-worm and the various species of cut worms. 

 Indeed, at times the work of these sod web-worms does resemble the 

 work of some of the cut worms hereinafter described. However, with 



