THE SO-CALLED TOBACCO WIREWOEM IN VIRGINIA. 9 



Table IV. — Duration of egg stage of the tobacco C'rambus, Appomattox, Va., 1910. 



Lot 

 No. 



Eggs laid— 



Eggs hatching — 



Incuba- 

 tion 

 period. 



Lot 

 No. 



Eggs laid— 



Eggs hatching— 



Incuba- 

 tion 

 period. 



1 



1910. 



July 7 



July 11 



July 12 



July 13 



July 25 



July 26 



Aug. 11 



1910. 

 July 12 



Dai/s. 



5 

 8-9 



7 

 6-7 



6 

 6-7 

 5-6 



8 

 9 

 10 

 11 

 12 

 13 



1910. 



Aug. 12 



Aug. 13 



1910. 



Aug. 17-18 



do 



Days. 

 5-6 



2 



July 19-20 



July 19 



4-5 



3 



Aug. 14 



Aug. 15 



Aug. 16 



Aug. 17..- 



Aug. 19-20 



Aug. 20 



5-6 



4 



July 19-20 



July 31 



5 



5 



Aug. 21-22 



Aug. 23-24 



5-6 



6 



• 7 



Aug. 1-2 



Aug. 16-17 



6-7 



HABITS OF THE LARVAE. 



NATURAL FOOD PLANTS. 



Larvae of the tobacco Crambus have been found feeding on the 

 following wild plants : 



Buckhorn plantain (Plantago lanceolata). 

 Oxeye daisy (Chrysanthemum leucanthe- 



mum). 

 Wild aster or "stickweed"' (Aster eri- 



coides and other species). 



Wild carrot (Daucus carota). 

 Sheep sorrel (Rumex acetosella). 

 Senecio (Senecio jacobgea) . 

 White-top (Erigeron annuus and other 

 species) . 



The first two plants named, the buckhorn plantain and the oxeye 

 daisy (PI. II, fig. a), were found to be the main food plants of the 

 larvae in the localities studied. The eradication or control of these 

 weed pests, therefore, will result in comparative immunity from loss 

 by this insect. Both species of plants have been found heavily 

 infested in many localities in widely separated sections. During 

 early spring the plantain seems to be the preferred food plant; later 

 a heavy infestation occurs on both plantain and daisy. 



On July 8, 1910, 23 out of 25 oxeye daisy plants examined in a 

 weedy field were infested, there being a total of 69 larvae about the 

 roots. As many as 20 larvae have been collected from one plant of 

 the oxeye daisy. 



In tobacco-growing sections of Tennessee and Kentucky white-top 

 is a frequent food plant. 



When meadows are plowed up and planted to tobacco there is 

 frequently serious injury from the "wireworms." (See PL II.) 

 Where such injury has occurred the weeds mentioned above have 

 invariably been found abundant in the sod, which explains the pres- 

 ence of the "worms." Injury has not been observed where there had 

 been previously a clean growth of grass or clover. Attempts to rear 

 adults from larvae confined in field cages containing only timothy and 

 clover resulted in failure, although the larvae lived for a considerable 

 time without other food. 



30183°— Bull. 78—14—2 



