18 



THE ARMY-WORM. 



thing their own way. By watching them after dark we 

 may see numerous black beetles chasing and grabbing them 

 with their large and pointed mandibles ; and after sucking 

 them dry, dropping them for other victims. 



A large number of birds are attracted to invaded fields 

 and, though the worms usually hide during the day, they kill 

 large numbers of them. Our best friends in exterminating 

 these noxious worms are, however, such nocturnal mammals 

 as shrews, skunks, weasels, and even gophers, which devour 

 large numbers. Considering all these facts we realize that 

 notwithstanding the vast number of worms in such armies 

 but comparatively few of them reach the adult stage, and it 

 is the experience of most observing people that one army- 

 worm season is not usually followed by another one. 



The life-history of armj^-worms is essentiall3' that of the 

 common cut-worms. In reality they 

 are nothing but cut-worms crowded 

 together in large numbers by favor- 

 able conditions, and doomed, on that 

 account, to suffer. Arm\'-worms can 

 be found in ever3' season, but in nor- 

 mal 3^ears thc}^ do not act as army- 

 worms, but lead the life of a common 

 cut-worm. The adult insects, one of 

 which is illustrated in fig. 11 (plate 

 II), fly in Minnesota from the middle of June till 

 late in September, in fact some have been captured 

 as earl3' as Ma\' 19th and as late as Sept. 29th. In some 

 cases large numbers are attracted to fermenting liquids, 

 while at other times only solitary specimens can be seen. It 

 is usuall^^ claimed that there are two annual broods of these 

 insects in Minnesota, but we have been unable to verifj^ this 

 statement, and onh^ know from experience that we can ex- 

 pect arm^'-worms in a summer following a wet spring. 

 Why this is so is not known. The metamorphosis of the 

 armj'-worm can be given in a few words: the eggs, which 

 are deposited early in the night, are thrust b\' means of a 

 horny ovipositor between the folded sides of a blade of grass; 

 usualh' fifteen or twent\^ eggs are glued together. Each fe- 



Fig. 10, — Ophion purga- 

 tum Sav, natural size. 



