INSECTS INJURIOUS TO CORN, 



247 



or the forepart of August. Just before the larvae transform to pupae, 

 they wriggle their bodies and pack the earth away from the same, so as 

 to make a little earthen cell, inside of which the pupa stage is passed. 

 The pupae transform to adults along the latter part of August, but 

 remain in these earthen cells, as a rule, over winter and until the fol- 

 lowing spring. 



The larvae of these wireworms, like those of practically all other 

 species, are extremely hard indeed to kill by any of the arsenical poisons. 

 They will eat arsenic, strychnine, etc., without any apparent ill effects, 

 so that the theory that these insects can be poisoned by soaking the corn 

 and rolling it in arsenic or strychnine or other poison before planting has 

 no value whatever. It is absolutely impossible to kill these insects out 

 in the field by any poison method known. The larvae, or wireworms, are 

 also extremely tough, so that one may step upon them upon the ordinary 

 soft ground and not injure them at all, as they will be pushed into the 

 soil before being crushed. When these larvae transform to pupae, how- 

 ever, the pupae seem to be unusually delicate and are easily killed by 

 simple disturbances which would not injure in any way the pupae of 

 most insects. Even the rupturing of their earthen cells is frequently 

 sufficient to kill them, and the thorough disturbance of the earth, such 

 as takes place in plowing and harrowing, will kill the most of them. 

 This is also the case with the young beetles when they first emerge from 

 the pupae. They are very soft bodied, of a light yellow color, and are 

 easily killed by any great amount of movement of the soil. They very 

 gradually indeed attain a hard covering and their dark coloring. The 

 adult of the corn wireworm when fully matured and in its normal con- 

 dition is represented in figure 5, enlarged four and one-half diameters. 

 It is brownish fuscous in color, the upper part of the thorax being densely 

 punctated and the sides shiny. They are about one-third of an inch 

 or a little over, in length, and are our most common adult wireworms 



Fig. 8. — A Common Wireworm : Adult and larva, enlarged ; and young larvae 

 feeding on roots of grass. The line below the beetle indicates its natural size. 



