THE HORSE-RADISH FLEA-BEETLE. 



DESCRIPTIVE. 



THE ADULT. 



In appearance PhyUotreta armomciae is distinct from any species 

 of flea-beetle belonging to or introduced into this country. It is 

 somewhat larger and wider than 

 any of the native species of the 

 genus. It is of oval form, 

 strongly convex, and black in 

 color. The first three antennal 

 joints, the apices or tips of the 

 four anterior femora, the tibise, 

 and the tarsi are reddish yellow. 

 The elytra are very light yel- 

 lowish, or cream color, nearly 

 white, with a very thin black 

 lateral margin and a broadened 

 sutural stripe, widest at the mid- 

 dle and constricted at each end 

 and extending from the base of 

 the thorax to the apex of the 

 elytra, where it joins the lateral 

 line. The frons or front is very 

 finely, and the prothorax and 

 elytra densely, punctate. A 

 sensitive pore from which pro- 

 ceeds a seta is located on the 

 lateral margin, which is behind 

 the anterior angle. In the male 

 the fourth antennal joint is 

 slightly thickened and longer 

 than the fifth. In the female the 

 fourth and fifth joints are equal. 



The average length is from 3 

 to 3.3 mm., but individuals have 

 been observed where there is a variation of from 2.6 mm. to 3.4 mm. 

 and a variation in width of 1.3 mm. to 1.9 mm. 



The following synonymy is recognized : 

 PhyUotreta armoraciae (Koch). 



Haltica armoraciae Koch, Entom. Hefte. v. 2, p. 75, 1803. 

 Haltica vittata Steph., Manclibulata. p. 292. 1831. 



The species is also treated systematically by Illiger, Duftschmidt. 

 Gyllhenhal, Schilling, Eedtenbacher, Seidlitz, Foudras, Allard, Lees- 

 berg, and others. 



Fig. 2. — Work of the horse-radish 



beetle in leaf petioles of horse-radish. 



(Original.) 



