INJURIOUS TO CABBAGE AND CRUCIFEROUS CROPS 375 



The Spinach-aphis or Green Peach-aphis * 



Another species of aphis often becomes destructive to cabbage, 

 spinach, celery and lettuce, as well as various greenhouse crops. 

 In the fall it migrates to peach, and is also known as the green 

 peach-aphis, as which it is discussed on page 658. 



Flea-beetles t 



A considerable number of small flea-beetles attack cabbage and 

 other cruciferous crops, and although as a rule only troublesome, 

 they appear periodically in enormous numbers and do serious 

 injury. They are mostly small species (there being seven species 

 of the genus Phyllotreta alone) not over an eighth of an inch long. 

 One of the most common throughout the country is the striped 

 turnip flea-beetle. J It is polished black with each wing-cover 

 marked with a broad, wavy band of pale yellow. The microscopic 

 white eggs are laid in a little excavation of the root near the crown 

 of the plant. The larvse mine into the roots and have been 

 reported to do considerable injury to them, but it seems probable 

 that most of them live upon the roots of cruciferous weeds. The 

 full grown larva (Fig. 270, a) is about three-eighths inch long, 

 quite slender and tapering, yellowish white, with brown head and 

 anal plate, and with marks on the thorax and transverse rows of 

 minute hair-bearing tubercles as shown in the figure. The West- 

 ern cabbage flea-beetle is the more common from the Dakotas 

 southward to Mexico and westward to southern California. It is a 

 uniform deep olive-green, with the surface irregularly punctate, 

 and 7 /ioo inch-long. Another species almost indistinguishable from 

 the first species above, is the wavy-striped flea-beetle, ^[ whose larvae 

 mine in the leaves of wild pepper grass (Lepidium virginicum), 



* Myzus persicce Sulz. See footnote on page 658. 



t Family ChrysomelidcE. Refer to pages 296, 335, for other flea-beetles. 

 -See. C. V. Riley : Report U. S. Commissioner Agr., for 1884, pp. 301-308. 

 I Phyllotreta vittata F'ab. 

 Phyllotreta pusilla Horn. 

 If Phyllotreta sinuata Steph. (zimmermani Crotch.) 



