Nov. 5, 192 1 



Pale Western Cutworm 



297 



four had 8. According to the rearing records of other larvae than those 

 shown in the table, several individuals passed through 9 larval instars 

 and one passed through 10. Eight instars, however, is the usual number 

 and the minimum is 7. 



Table III. — Duration of larval instars of Porosagroiis orthogonia under insectary 



conditions 



Larva record No. 



Number of days in each instar. 



IV. 



VII. VIII. 



Num- 

 ber of 

 days in 

 larval 

 stage. 



2ia 



2lb 



SIC 



2 id 



2ie 



Da 



Db 



Dc 



Dd 



De 



42a 



42b 



42c 



42d 



426 



Ma. 



Mb 



Mc 



Md 



Me 



Average 



12 

 12 



9 

 12 



13 

 12 

 12 



13 

 II 

 10 



14 

 12 



13 

 9 



7 

 13 

 13 



7 



5 

 6 

 6 

 9 

 7 

 9 

 9 

 10 



7 

 9 

 8 



5 



10 

 8 

 II 

 6 

 7 

 9 

 12 



7 



II 



8 



10 



10 



7 



9 



12 



12 



9 

 10 

 II 



7 



8 



10 



9 

 12 

 10 



9 

 7 

 9 

 7 

 13 

 10 



14 

 10 

 10 



9 

 10 

 10 

 10 



15 



9 



10 



10 



12 

 10 

 14 

 9 

 II 

 II 

 II 



9 



10 



17 

 II 



9 

 18 

 12 

 12 



10 



13 



9 



9 



10 



13 

 13 

 18 



13 

 17 

 13 

 9 

 16 

 16 

 15 

 14 

 20 



17 

 12 



13 

 9 

 18 

 16 

 14 

 13 



9.4 



9.8 



II- 3 



14.4 



44 

 29 



32 

 16 



14 

 14 

 14 

 21 

 16 

 19 

 25 

 41 

 34 

 14 

 20 



18 

 18 

 26 



45 



37 

 48 



63 



45 

 51 

 32 



2>Z 

 33 

 75 

 56 

 65 

 43 



99 



85 



98 



124 



62 



125 

 121 



151 

 125 

 150 

 123 

 104 

 112 

 112 

 119 

 148 



144 

 148 



131 

 83 



22. 6 



29. 6 



118 



FEEDING HABITS OF LARVA 



The larva differs from that of most cutworms in its feeding habit in 

 that it almost invariably attacks the plant below the surface of the 

 ground. The most frequent type of injury is the eating away of the 

 central stem and its surrounding sheaths from }i inch to i inch below the 

 surface of the ground. In many instances the stem is severed and the 

 lower part not eaten, and frequently it is only slightly chewed into before 

 the worm moves on to another plant. Even slight injury to the under- 

 ground portion of the central stem usually results in the death of the 

 plant. A very small portion of each plant is actually eaten by this 

 cutworm, and its capacity for destruction is thus greatly increased. 

 The first indication of injury is the presence of wilting or dried plants 

 which can be easily lifted out of the soil without bringing the roots. 

 The destruction of grain that is just pushing through the ground is par- 

 ticularly rapid, one worm being able to cut off plant after plant in quick 

 succession. The worm usually moves along the drill row, taking each 

 plant as it goes (PI. 30, D). Where one crop has been destroyed and 



