328 MANUAL OF VECET ABLE-GARDEN INSECTS 



The IIorse-Radish Flea-Beetle 



Phyllotreta armoracice Koch 



Imported from Europe about 189.'], this horse-radish pest 

 is now present in the northern states from New York and New 

 Jersey to Iowa and Nebraska. It has also been found at 

 Montreal, Canada. In some localities it has already proved 

 itself a serious enemy of horse-radish, making it necessary to 

 replant the beds yearly. In contrast 

 to the habits of many other flea- 

 beetles, this insect has a very re- 

 stricted list of food plants, including 

 only marsh cress in afldition to horse- 

 radish. The winter is passed by the 

 beetles in dry sheltered places. The 

 adult (Fig. 207) is about i inch in 

 length, oval, strongly convex, black in 

 color, with each wdng-cover yellow^ish, 

 except a narrow black stripe along 

 the outer margin and a wider one on 

 the inner margin, the latter broadest 

 at the middle. The antenna? are 

 yellowish at the base. The legs are yellowish except the 

 hind femora and all but the tip of the front and middle 

 tibia% which are black. The beetles appear on the plants 

 early in the spring and eat out holes in the leaves and 

 cavities in the midribs. The female deposits her smooth, 

 oval, orange eggs, about ^V inch in length, in clusters of twenty 

 or more, loosely attached to the petioles of the young leaves. 

 Egg-laying begins in late April or May and may continue until 

 August. Each female usually lays several batches of eggs and 

 the total number laid by a single individual may exceed 400. 

 The eggs hatch in a week or two. On hatching, the young 



Fio. 207. — Tlie horse- 

 radish flcti-beetle (X 9). 



