THE WATER-CRESS LEAF-BEETLE. 19 



adults attack the cuticle of the stem after feeding on the leaves, as 

 has been noticed in the case of armoracice. E. A. Fitch has ob- 

 served the partiality of the latter for water cress and other crucif- 

 ers which grow in watery places and mentions the destruction of an 

 entire crop of horseradish. 



Kaltenbach " records, according to Gyllenhall and his own obser- 

 vations, Veronica heccahunga, Cardamine amara^ and Cochlearia 

 armoracia or horseradish as food plants, and states that the larva 

 undergoes metamorphosis in the earth, the pupa state lasting four- 

 teen days. Cornelius ^ is cited as having observed two generations, 

 the spring generation being found in May and June and the second in 

 September. Thomas H. Hart records the Avater starwort of England 

 {Callitvicha verna) as another host plant. T. R. Rillups,'^ an ento- 

 mologist as well as truck grower, mentioning this species as Phcedon 

 hetidcp., states that it is " one of the greatest insect pests the market 

 gardeners around London have to contend with." Our American 

 species undoubtedly hibernate as adults and appear in early spring 

 under boards and similar shelter. 



METHODS OF CONTROL. 



How to successfully control this insect under ordinary conditions 

 is quite a problem. Paris green was tried by our correspondent, 

 mixed with flour and sprinkled over the plants when the dew was on, 

 and this reduced the numbers of the insect somewhat. Owing to the 

 moist condition of the plants, however, the flour formed a paste 

 which stuck like glue, and it was therefore abandoned. Applied in 

 water it rolled oft' the plants. We were not informed if this appli- 

 cation Avas made Avith a spraying machine. If the plants were 

 sprayed lightly Avith a fine spray, it might ansAver, or, better, Paris 

 green dry Avith only 20 parts of flour, or plaster or air-slaked lime. 

 An arsenical should not be used Avithin about a Aveek of the time of 

 cutting the cress for nuirket. In the case of Paris green there is 

 practically no danger of poisoning cA'en if it Avere used later, as the 

 Avashing whicli is given the cress will carry aAvay all perceptible 

 traces of the poison. 



If conditions should be such that the pond or stream in Avhich 

 Avater cress infested by this species is groAving could be completely 

 OA'erfloAved, it Avould cause the insects to rise to the surface, and in the 

 case of running Avater Avould Avash them doAvnstream. Flooding 

 alone might not entirely solve the problem, as these beetles are able to 

 survive considerable immersion. 



When the cress is groAvn in sulliciently large bodies of Avater ex- 



a Pflanzenfeinde, p. 26; » Stett. Ent. Zeit., 1863, p. 123; cThe Entomologist, 

 Vol. XIV, 1881, p. 236. 



