24 



PEELIMINAEY BEPOET OK ALFALFA WEEVIL. 



of the season, however, during August, when the temperature is 

 higher, the pupal period averages only 3 days, the cocoon being spun 

 only about 36 hours before the larva pupated. The adult leaves the 

 cocoon about a day after transformation, and unlike others of this 

 genus does not devour the cocoon. Although the insect has passed 

 through its transformation from egg to adult the injury 

 it causes is by no means ended. The beetles them- 

 selves not only feed upon the young growth (fig. 8), 

 but gnaw off the bark of the stems, and, together 

 with the larvae still in the fields, in this way prevent 

 the alfalfa from springing up for weeks after the first 

 crop of hay has been removed. Two of such fields 

 are shown in Plate V, figure 3, and Plate VI, figure 3, 

 the ground being almost as bare of growing plants as 

 in figure 1, Plate VIII, where the ground has been 

 fig. 7.— The alfalfa ^orn U p w ith a spring-tooth harrow. The beetles some- 

 Muc°h l cniargxi' times cluster in great numbers upon a single plant, as 

 (Author's mus- illustrated in figure 8. 



tration.) 



FOOD PLANTS. 



In a series of experiments carried out by Mr. P. H. Hertzog, larvae 



of Phytonomus 'posticus were placed in cages on various food plants, 



both alone and with alfalfa, and it was found that they fed freely 



upon the following plants, in combination with alfalfa: 



Sweet pea, Laihyrus odoraius; Utah milk vetch, 

 Astragalus utahensis; string bean, Phaseolus vulgaris; 

 obtuse-leaved vetch, Vicia sp. ; narrow-leaved vetch, 

 Vicia sp. ; white clover, Trifolium repens; red clover, 

 T. pratensc; alsike clover, T. hybridum; yellow sweet 

 clover, Mcliloius indica(?) ; white sweetclover, M. alba; 

 Mrdicago lupulina; M. echinus; M. hispida nijra; M. 

 hispida confinis; M. hispida terebellum; M. muricata; 

 M. orbicularis; M. scutellata; black locust, Robinia 

 pseudacacia; fenugreek, Trigonellafcenumgrxcum. 



The following is a list of plants eaten by 

 the larvae when no other food was offered, but- 

 refused when offered together with alfalfa : 



Hedysarum mackcnzii; Astragalus oreophilus; downy 

 lupine, Lupinus;s-p. chickpea, Laihyrus sativus; Vicia 

 alropurpurea; Vicia dispem a; spring vetch, Vicia saliva 

 alba; hairy or winter vetch, Vicia villosa; spider plant, 

 Clcomc serrulala. 



The following plants were refused by the larvae even when no other 



food was offered : 



Everlasting pea, Laihyrus latifolius; round-leaved mallow, Malva rotundifolia; birds- 

 knot grass, Polygonum aviculare; garden pea, Pisum sativum; lamb's-quarters, Cheno- 

 podium album; purslane, Portulaca olcracea; prickly lettuce, Lactuca scariola, perhaps 

 var. irAcgrata; ground cherry, Physalis longi/oHa^); bitterweed, Ambrosia psilos- 

 tachya; bitterweed, Ambrosia trifidaintegrifolia; rough pigweed, Amaranthus retroflexus. 



Fig. 8.— The alfalfa weevil: Adults 

 clustering on and attacking sprig of 

 alfalfa. About natural size. (Au- 

 thor's illustration.) 



