8 BULLETIN 902, U. S. DEPARTMENT OF AGRICULTURE. 



When the beetles occur in great abundance they injure also sugar 

 beets and table beets {Beta spp.), mangel-wurzel {B. vulgaris var. 

 macrorhiza) , lettuce {Lactuca sativa), beans {Phaseolus spp.), peas 

 {Pisum sativum), carrots {Daucus carota), tomato {Lycopersicum 

 esculentum), potato {Solanum tuberosum) , and corn {Zea spp.). 



Injury is due to the beetles eating pitlike holes in the leaves 

 of young plants, usually selecting the lower surface. Radish is so 

 seriously attacked practically everywhere within the destructive 

 range of this pest that it is almost impossible in such regions to grow 

 this vegetable unless strenuous efforts are made to prevent the inroads 

 of the flea-beetle. Turnip and mustard are about equally attractive 

 to the beetles and unprotected beds are frequently destroyed. Impor- 

 tant injury to cabbage is confined to young plants in seedbeds or to 

 plants soon after they have been transplanted in the field. Horse- 

 radish is readily attacked and the foliage is often so completely 

 riddled that it has the appearance of a sieve when held up to the 

 light. This plant, however, is very resistant and the roots attain a 

 good growth in spite of severe attack to the leafage 



The larvae have been observed on radish, Cleome, and Lepidium 

 puhecarpum only, but doubtless live on the roots of many other 

 cruciferous and related capparidaceous plants. The injury done 

 by the larvae is negligible, so far as our observations go, in which 

 respect this species differs from the related striped cabbage flea- 

 beetle and horse-radish flea-beetle. 5 



SEASONAL HISTORY. 



In its more northern range the beetle passes the winter months 

 in hibernation under clods of earth, or under heaps of weeds, dead 

 leaves, or other rubbish, whence it comes forth with the first warm 

 days of spring. In the extreme South the beetles are active through- 

 out the year but reproduction does not occur during the winter. 

 In the Arkansas Valley the beetles issue from their winter quarters 

 during the latter part of March or early April. At first the foliage 

 of Sophia pinnata and horse-radish supply them with food. From 

 these plants they go to early mustard and radish, and throughout 

 the season or until severe freezes have occurred the beetles are to be 

 found on various cruciferous vegetables and weeds. In south Texas 

 beetles occur afield from February until December, being found, with 

 the exception of two months, practically throughout the year. 



There are apparently three generations annually in Otero County, 

 Colo. Egg laying begins within a few days after the beetles leave their 

 winter quarters — as early as April 14 — and continues until early 

 September. 



5 Phyllotreta vittata Fab. and Ph. armoraclae Koch, respectively. 



