THE WATER-CRESS LEAF-BEETLE. 



(Phiedon icruginosa Siiffr.) 



By F. H. Chittenden, 

 Entomologid in Charge of Breeding Experiments. 



INJURIOUS OCCURIIENCE. 



Among plant-feeding native insects which have recently appeared 

 in new roles is a little blackish leaf-beetle, Phadon ceruginosa Suffr., 

 which was reported for the first time as injurious to water cress 

 {Nasturtium, officinale) in Pennsylvania, in 1903, 



During September Mrs. Hannah B. Hannum, Brandywine Summit, 

 Pa., sent larva? and adults of this species, with statement that they 

 were devastating her water-cress pond. Both larvae and beetles fed 

 chiefly on the lower side of the leaves. In confinement they con- 

 tinued feeding, attacking the stalks also. The larvae all reached 

 development about the same time, being fully matured September 11 

 and 12, on the last of these two days crawling about the rearing jar 

 and ceasing to feed. The pupal period was not observed, but it 

 probably lasted ten days or a fortnight, as the weather was cool. 

 The beetles continued for some time in our rearing cages, frequently 

 pairing, but depositing no eggs. 



August 19, 190-1, Mrs. Hannum sent additional specimens of this 

 species in the beetle and nearly grown larval stages. It was noticed 

 that the beetles did not swim rapidly, but steadily, and they were 

 seemingly not discomposed by being somewhat out of their natural 

 element. It seems probable that they fly from plant to plant, and 

 like most beetles undoubtedly are able to float for many hours, and 

 perhaps even swim short distances until they reach a landing i^lace. 

 September 13 our correspondent sent still another lot of this species, 

 mostly beetles, but a number of larvae were included. 



Specimens of the larvae of a syrphus fly accompanied this sending 

 and probably fed at times on the small larvae of the beetle. 



DESCRIPTIVE. 



The 'beetle. — This species belongs to the tribe Chrysomelini of the 

 family Chrysomelidae. It is classified in our publications on the 

 Coleoptera of America north of Mexico with Plagiodera, but Eu- 

 ropean systematists place allied forms in the genus Phaedon Latr., 

 which now comprises seven species occurring in our country. The}?^ 

 are very small semiglobose forms. The outline is oval, with the thorax 

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