126 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 10 



knowledge of that field was unusually complete. In April the greater 

 part of the field was inadvertently flooded with sediment, and from 

 that time there were too few weevils in the field to answer the purpose 

 of the experiment, while they attacked neighboring fields as usual. 

 Since mere submergence in water has practically no effect upon the 

 insect at any stage, ordinary irrigation is ineffectual. Similar results 

 can be produced by dragging a muddy field, but the effect upon the 

 soil is disastrous. Since only a limited number of fields can be flooded 

 in the way that I have described, its usefulness is limited to that extent. 

 Where it can be practiced it is successful. 



Spraying 



Among methods of wider usefulness, spraying was one of the earliest 

 to be considered. It was tried by the Utah Experiment Station, 

 before the Bureau of Entomology took up the investigation, and was 

 then reported favorably, but later discarded. It has since been further 

 investigated and, while not yet perfected, it promises practical success. 



The theory of spraying for the alfalfa weevil embraces two possibil- 

 ities; namely, poisoning the old adults and new-hatched larvae in early 

 spring, and the full-grown larvae and new adults in summer. Adults 

 which have survived the winter begin to deposit eggs soon after warm 

 weather arrives, at first confining their work to the dead stems of 

 various sorts which litter the ground, but later ascending the green 

 plants and ovipositing in them. Meanwhile, they feed sparingly upon 

 the epidermis of leaves and stems and also use their beaks in preparing 

 holes to receive the eggs. Although they consume but little tissue, 

 they take it chiefly from the surface, and although they cease feeding 

 after taking an amount of poison too small to produce immediate death, 

 it causes them to cease ovipositing. It is probable that they feed also 

 upon the dead stems. Poisoning the adults is therefore feasible and 

 effective. 



Many eggs which have been deposited unseasonably early, either in 

 the spring or the previous fall, hatch before the main economic attack 

 begins, and are numerous enough to constitute a separate problem. 

 These early larvae are easily poisoned by the same application which 

 destroys the adults, and are prevented from hindering the more im- 

 portant purpose of the treatment. In these two ways, the early 

 spraying protects the crops throughout the season, and in some meas- 

 ure through the following year as well, so that a successful spraying 

 experiment sometimes renders the fleld unfit for similar work the next 

 year. 



The second possibility is in spraying the stubble after the first crop 

 has been removed. It is unnecessary after a successful early spray, 



