4 MASS. EXPERIxMENT STATION BULLETIN 261 



adults. At first they feed in colonies near the old egg mass on the lower sur- 

 face of the leaf, but soon become scattered as they crawl to other leaves in 

 search of food. They consume the lower layers of the leaf, leaving the upper 

 epidermis and large veins. The upper tissue soon dies and bleaches out, leav- 

 ing a whitish skeletonized appearance (Plate I, A). 



Seasonal History 



The adults of the Mexican bean beetle emerge from hibernation in the 

 spring after the advent of warm weather, and locate suitable food plants, 

 principally beans. Egg-laying begins in about a week or ten days after their 

 appearance, the eggs generally being attached to the under side of the leaves. 

 Incubation of the eggs requires about ten days to two weeks. The larvae feed 

 upon the leaves and pods for about three to five weeks, then attach themselves 

 to the leaves and pupate; the adults emerge eight to twelve days later. The 

 number of generations in a season is dependent upon the climatic conditions 

 and length of season, varying from one to four in the different localities. The 

 beetles enter hibernation in the fall in moist places, remaining dormant or 

 semi-dormant, depending upon the region, until spring. 



Food Plants 



The bean beetle is primarily a bean pest, attacking by preference the com- 

 mon beans, including bush and pole varieties of snap beans, pinto, navy, lima, 

 and tepary beans. It can subsist on a number of other plants and has severe- 

 ly injured cowpeas and soybeans in several states. Howard and English 

 (1924) list the following plants as being attacked: 



Common Name Scientific Nam,e 



Tepary bean Phaseolus acutifolius 



Garden bean P. vulgaris 



Including navy, pinto, kidney, pole beans, etc. 

 Lima bean P. lunatus 



Beggarweed Meibomia tortuosa, 



M. canescens, 



M. viridiflora 



Hyacinth bean Dolichos lablab 



Cowpea and Black-eyed Pea Viffna sinensis 



Soybean Glycine hispida 



Adsuki bean Phaseolus annularis 



Alfalfa Medicago sativa 



Sweet clover Melilotus alba 



Distribution 



The bean beetle is a native of southwestern United States and Mexico. In 

 the West it is now found in Wyoniing, Utah, Colorado, Arizona, New Mexico, 

 and Texas. It was discovered in Alabama in 1920 and has increased its range 

 rapidly to the north and east since then. It spread to Georgia, Tennessee, 

 North and South Carolina, and Kentucky in 1921; Virginia in 1922; We«t Vir- 



