THE SO-CALLED TOBACCO WIREWORM IN VIRGINIA. 



the latter part of June, but moths are not abundant until about the 

 third week in July. From this time their numbers gradually increase 

 until about the second week in August, when they are exceedingly 

 numerous, at times appearing almost in swarms in weedy fields when 

 disturbed. From the middle of August there is a rapid decrease and 

 after the 1st of September only an occasional one can be found. 

 Table I gives dates of emergence of moths from some of the field 

 cages at Appomattox in 1910. 



Table I. — Emergence of moths of the tobacco Crambus in outdoor rearing cages at Appo- 

 mattox, Va., 1910. 



Larvae col- 

 lected— 



Food plant on 

 which found. 



Moth 

 emerged — 



Larvae col- 

 lected— 



Food plant on 

 which found. 



Moth 

 emerged — 



1910. 





1910. 

 July 2. 

 July 21. 

 July 22. 

 Aug. 3. 

 July 3. 

 July 14. 

 July 22. 

 July 23. 

 July 26. 

 Aug. 1. 

 July 29. 



1910. 



June 26 



Do 



Do 



Do 





1910. 



July 18. 



Do 



do .. 



Wild carrot 



Tobacco 



Aug. 13. 



Do 



do 



Aug. 6. 



Do 



do... 



do 







do 



June 28 



Do 



Do 



Julyl 



Do 



Do 



Plantain 



July 14. 



Do 







Aug. 15. 



Do 



Do... 



Senecio 



Aster (stickweed) . 



Aug. 7. 

 July 29. 











Do 







July 27. 



Do... 















The females die soon after egg laying is finished. There is appar- 

 ently only one generation a year, the eggs hatching in summer and 

 the larvae completing their growth during the follow- 

 ing year. The greater number of larvae are in the pupal 

 stage during the first halt of July. 



DESCRIPTION. 



THE EGG. 



The egg (fig. 2) is creamy white when first deposited, but grad- 

 ually assumes a pinkish shade, which deepens to orange rufous 

 before hatching. The average length is 4 mm. and the diameter 

 0.32 mm. It is regularly oval, with the ends slightly truncate, 

 and has a polished appearance. There are about 18 longitudinal 

 carinee and numerous transverse striae. 



THE LARVA. 



FIRST INSTAR. 



When first hatched, the body of the larva is semitransparent, and the alimentary 

 canal can be plainly seen. The outline of the body, when seen from above, is almost 

 triangular. The larva is white, or pale yellowish white, and about 1 mm. long, with 

 a few scattered, light-colored hairs on the head and body. The head shield measures 

 0.15 mm. in width, is yellowish brown, and moderately bilobed, with the clypeus 

 attaining the apical third. The cervical shield is tinged slightly with brownish. 

 Five pairs of prolegs occur on the 7th to 10th segments, inclusive, and on the 13th 

 segment. 



LAST INSTAR. 



The full-grown larva (figs. 3, 4) is about 15 mm. long, and yellowish white, with a 

 tinge of pink dorsally. The hairs of the body are slender, brownish, and set on large 

 fuscous tubercles. The head shield measures 1.2 mm. in width, and is pale yellowish 



Fig. 2.— The to- 

 bacco Crambus: 

 Egg. Greatly 

 enlarged. (Origi- 

 nal.) 



