ZOOLOGICAL DEPARTMENT. 303 



crops of New England and New York, at which time Dr. Asa Fitch fully 

 described it in his sixth report. In 1866 and again ten years later it did 

 great damage in various sections of the west. We see then that this louse 

 does not come yearly but only at long intervals. Why is this? It is doubt- 

 less owing in some measure to the weather, but more to its insect enemies. 

 We readily see that its enormous prolificness would make it as the sands of 

 the sea shore every year, except that some natural agent held it in check. 

 Fitch describes three such enemies. Even now as we visit the oat and wheat 

 fields we find many forms different from any previously described. These 

 have short, rounded bodies, which are of a dirty white color. The cause of 

 this is that these are attacked by parasites, which are eating them up. We 

 have reared several of these little benefactors, and find them now busily 

 engaged in the fields laying the eggs that will destroy the lice. These minute 

 parasitic insects lay a great many eggs, one in each louse, and their presence 

 and prosperity mark the doom of the lice. Thus through the agency of these 

 minute parasitic forms, aided by climatic influences, we are to be saved from 

 a raid by this grain aphis next year, and will be greatly benefited this year. 

 Indeed, in some cases, these little friends will very likely save us from serious 

 damage. Why the parasites are not able to come successfully to the rescue 

 each year is still unknown. Very likely this problem will receive a very 

 valuable practical solution in the future. In these parasites the ento- 

 mologist sees the doom of the lice, but not, I fear, till great harm is done. 

 Dry weather is a great promoter of insect productiveness. It is more than 

 probable that the exceeding drought of 1887, 1888 and of the April and 

 May just past, together with the mild winter of 1888 and '89, have had 

 much to do with the present invasion. We might expect much aid from our 

 frequent June rains, but I fear they were too late. Observation shows that 

 the lice are more than holding their own, so we may conclude that the warm 

 rains are not greatly depleting their ranks. 



WHAT TO EXPECT. 



Where the lice are very numerous, as they seem to be over a widespread 

 area of our country, they must do great injury. Where ten or twelve lice 

 are collected about a single kernel of wheat, as I have actually seen in the 

 past few days, there is little hope for that kernel. I have counted one hun- 

 dred and sixty lice on a single head of wheat. It is hoping too much of 

 the little parasitic flies to expect them to save the present crop. We can but 

 expect much injury, especially where the lice are in such countless numbers 

 as are now seen in many of our wheat fields of Indiana, Ohio and Michigan. 



WHAT OF REMEDIES. 



The excellent specific against plant louse ravages, the kerosene and soap 

 mixture, cannot be used without much injury to the crop. To apply it 

 might be like the jump from frying pan to fire. Again, the lice are so pro- 

 tected by the close cluster of the kernels that very likely the remedy would 

 not be fully effective. I could not, therefore, recommend its application in 

 this case. We are now making extensive and accurate experiments, so that 

 at time of a future raid we can speak with positiveness in this matter. We 

 are aiming to find just what the damage is, just how many lice it requires 



