CUTWORMS, ARMYWORMS, AND RELATED SPECIES 13 



Many larvae collected in the field for rearing in the laboratory died 

 of a disease that turned them black. This was termed "r earing disease." 

 Dead larvae having somewhat the same appearance were noted in 

 the field after heavy rains. 



TUNNEL-MAKING CUTWORMS 



Four species of cutworms have the habit of making tunnels in the 

 moist soil near their host plants, where they hide during the day. At 

 night they come out, cut off pieces of the foliage of their host plants, 

 and take this food into their tunnels. 



Agrotis gladiaria (Morrison) 



(Figs. 2, A; 4, F; 7, D) 



Distribution. — This species is generally distributed in the United 

 States and Canada east of the Rocky Mountains. 



Economic status. — In the central Great Plains this cutworm occa- 

 sionally becomes abundant in pasture lands and alfalfa but, so far as 

 is known, does not reach destructive abundance. It has been reported 

 as being very destructive in Illinois and Kentucky at times. 



Food plants and larval habits. — The larvae feed on a large number of 

 plants, and are especially fond of corn and clover. In the Plains region 

 the species occurs chiefly in grasslands. The larvae appear to be par- 

 ticularly sensitive to light, and exposed larvae frantically attempt to 

 gain cover. Crumb (5) states that the larvae make permanent tun- 

 nels in the soil, with an opening near the plant attacked. 



Seasonal history. — There is but one generation annually. The moths 

 emerge in September and deposit their eggs soon thereafter. The eggs 

 hatch in the fall, and the winter is passed as a partly grown larva. In 

 Kansas the larvae are full-grown by the middle of April and soon begin 

 to construct their pupal cells, in which they estivate until pupation 

 begins in August. The adults begin to appear early in September, 

 the heaviest flight occurring late in September and early in October. 



Life cycle. — Eggs deposited on October 6 hatched in 12 days. All 

 the larvae molted six times and three molted seven times. The periods 

 required in the various stages and the width of the head capsule in the 

 different larval instars were as follows: 



Stage: Period, Width of head 



Instar: (days) capsule (mm.) 



First 11 to 16 0.35to0.40 



Second 6 to 10 .50 to .55 



Third •___ 10 to 107 .70 to .83 



Fourth 32 to 114 .90 to 1.30 



Fifth 14 to 49 1.40 to 1.80 



Sixth 11 to 17 1.80 to 2.45 



Seventh 12 to 172 2.60 to 2.75 



Eighth i 136 to 172 



Total 314 to 356 



Pupa 27 to 40 



Egg to adult 358 to 403 



1 For 3 individuals having 8 instars. 



