INJURIOUS INSECTS. 115 



It is a curious and interesting fact that one species of insect may 

 be very abundant one 3'ear and another the next and so on for 

 several years, when the species that was abundant on some former 

 3'ear will be abundant again, and so they go on. Some years ago 

 my home was where I had the exposure of broad grass fields, and 

 all summer long more or less of the night was spent in collecting 

 insects, either at molasses put on a fence in spots to attract them, 

 or at a strong light in a window. One year there would be a few of 

 a large number of diflJ'erent species, but one species would be so 

 very abundant as to be a perfect nuisance both at the light and 

 the molasses, while the next year the same would be true, but a 

 different species was usually abundant, and so they went on, 

 apparently taking turns. 



These insects belonged mainly to the family Noctuidce and some 

 of them were the most notorious of cut-worms. During one 

 season, the army-worm moth was so exceeding!}' abundant that I 

 wondered the farmers had not noticed their injury to the grass crops 

 in that vicinit}^ and I felt sure that the next season there would be 

 an invasion of the arm^'-worm^ ; but, strange to sa}', not a solitary 

 arm^'-worm moth did I capture that season. What could have 

 caused such a complete extermination of that species in so short a 

 time, I am at a loss to conjecture. I feel sure that I have ^-et 

 something to learn about the arm3'-worm. 



The various species of this family- which I captured there were 

 feeding on the different forage plants grown on those fields for 

 ha}'. The cut-worms proper came up by night aud ate off the 

 stems of clover, while others devoured the leaves of the grasses, 

 but if they had come up in the cultivated lands and eaten off a 

 cabbage plant here and there, what a hue and cry would have been 

 made about it ; yet those farmers never dreamed that anything 

 was amiss down in the grass fields, while my captures indicated 

 that not less than a quarter part of all their hay crop was devoured 

 every year. 



The salvation of such fields from the insects would be to culti- 

 vate them ; and, by a rotation of crops, starve the insects out. 

 The insects that feed on the various grasses do not feed on pota- 

 toes, and if a grass field that is infested with certain species of 

 insects be plowed up and cultivated for a year or two and potatoes 

 or some other crop as unlike the grasses as possible be planted, 

 the grass insects will die out or move to other quarters ; aud if the 



