272 MAINE AGRICULTURAL EXPERIMENT STATION. 1917. 



(i) Eaten readily. 



Willow, Salix sp. near nigra Marsh, 5. cordata Muhl. ; aspen pop- 

 lar, Populus tremuloides L. ; balsam poplar, Populus balsamifera 

 L. ; alder, Alnus incana (L.) Moench. 



The form of the scientific names and the sequence of the plant 

 families in the above tables follows the use of the last edition of Gray's 

 Manual. 



The writer has found the following references to additional 

 host-plants in the literature : 



Alder. Alnus serrulata Willd. [Now classed as nu.osa (DuRoi) 

 Spreng.] 



Harris (1869); Lititner (1887); Packard (1890). 

 Knotweed and smartweed. Blatchley (1910). 



ACTIVITIES OF THE ALDER FLEA-BEETLE. 

 FEEDING HABITS OF THE LARVA. 



The larvae live exposed on the leaves of their food-plants, 

 on either surface. In the case of the alder, when they first 

 hatch they crawl to the petiole end of the leaf, where they feed 

 for a few days protected under the slightly revolute margin. At 

 first the larvae eat only the lower epidermis and the green tissue, 

 leaving the upper epidermis ; but before this instar is over, they 

 eat this epidermis also, leaving only a skeleton of the larger veins. 

 This perfect and beautiful skeletonization, which has also been 

 remarked upon by Harris (1869), Lintner (1887), and Pack- 

 ard (1890) is characteristic of all of the larval feeding, with the 

 exceptions here noted ; it is illustrated in figure 29. The nearly 

 full grown larva eats holes through the leaves, as does the adult. 

 The skeletonization is not as perfect on the leaves of the balsam 

 poplar or the willow, as it is in the case of the larva. A balsam 

 poplar leaf skeletonized by the larvae of Altica bimarginata is 

 shown in figure 31. 



THE FEEDING HABITS OF THE ADULT. 



The adult beetles feed very freely on the leaves of the alder, 

 eating little holes through them. This method of feeding, which 

 is as characteristic as that of the larvae, is illustrated in figure 

 30. The adults feed both in the fall and in the spring. Willow 

 and balsam poplar are attacked in the same way, and in no case 

 do the adults ever skeletonize the leaves. 



