24 
PRELIMIXAEY REPOET OIsT ALFALFA WEE\T[L. 
Fig. 7.— The alfalfa 
weevil: Pupa. 
Much enlargrd. 
(Author's illus- 
tration.) 
of the season, however, durmg 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 remoTed. Two of such fields 
are shown in Plate Y, figure 3, and Plate YI, figure 3, 
the ground being almost as bare of growing plants as 
in figure 1, Plate YIII, where the ground has been 
torn up with a spring-tooth harrow. The beetles some- 
times cluster in great numbers upon a single plant, as 
ulustrated in figure 8. 
FOOD PLANTS. 
In a series of experiments carried out by Mr. P. H. Hertzog, larvae 
of PJti/tonomus posticus were placed in cages on various food plants, 
both alone and T\dth alfalfa, and it was found that they fed freely 
upon the foUo^ving plants, in combination ^\dth alfalfa: 
Sweet pea, Lathyrus odoratus; Utah milk vetch, 
Astragalus uiahensis; string bean, Phaseolus viiljaris; 
obtuse-leaved vetch, Vida sp. ; narrow-leaved vetch, 
Vicia sp.; white clover, Trifolium repens; red clover, 
T. pratense; alsike clover, T. hybndum; yellow sweet 
clover, Melilotitsindica{?);vrhitesweetcloveT, M.alba; 
Medicago liipulina; M. echinus; M. hispida nigra; M. 
hispida confinis; M. hispida terebellum; M. muricata; 
M. orbicularis; M. scutellata; black locust, Eobinia 
pseudacacia; fenugreek, Trigonella foenumgraecum. 
The following is a list of plants eaten by 
the larvae whenno other food was off ered,but 
refused when offered together with alfalfa: 
Redysarum machenzii; Astragalus oreophilus; downy- 
lupine, Lupinus ; sp. chick pea, Lathyrus sativus; Vicia 
atropurpurea; Vicia dispema; spring vetch, Vicia sativa 
alba; hairy or winter vetch, Vicia villosa; spider plant, 
Cleome serrulata. 
The following plants were refused by the larvae even when no other 
food was offered : 
Everlasting pea, Lathyrus latifolius; round-leaved mallow, Malva rotundifolia; birds- 
knot grass. Polygonum aviculare; garden pea, Pisum sativum; lamb's-quarters, Cheno- 
podium album; purslane, Portulaca oleracea; prickly lettuce, Lactuca scariola, perhaps 
var. integrata; ground cherry, Physalis longifolia(?)] bitterweed, Ainbrosia psilos- 
tachya; bitterweed, Ambrosia trijidaintegrifolia; rough pigweed, Amaranthus retrofiexus. 
Fig. 8.— The alfalfa weevil: Adults 
clustering on and attacking sprig of 
alfalfa. About natiiral size. (Au- 
thor's illustration.) 
I 
