FOOD PLANTS. 27 
place in whatever location the prepupa may be, and the transparent 
and delicate empty skin is found behind the pupa. It was observed 
during the fall that pupae exposed to a low temperature did not com- 
plete their development to the adult stage. These, when later placed 
in the greenhouse, changed to adults unless exposed to the unfavorable 
conditions too long, when all were killed. 
During the pupal stage several external changes take place. At 
first the ocelli are not evident, but as the pupa develops these become 
prominent in a triangle between the folded antennae. Then the reticu- 
lations of the body begin to appear, and within two days of the 
emergence of the adult the pupa begins to darken and the legs, 
antennae, and wings begin to show blackish bands. The adult 
emerges in a manner similar to the molting of the larva. Emergence 
has been noted at all hours of the day, and there seems to be no par- 
ticular time for its occurrence. 
FOOD PLANTS. 
This insect seems to be nearly as omnivorous as the onion thrips, 
as the following list of food plants upon which it has been reared or 
observed during the past two years by the writer would indicate. 
These have been divided into economic and wild food plants, and 
under each will be given notes on injury and appearance of injured 
plants. 
BEANS. 
The injurious occurrence of this insect on the foliage of beans gives 
to it its common name. It has been observed by the writer to feed on 
bean foliage in the adult and larval stages from early in February, 
in sheltered places, until the plants are killed by frost in the fall. 
In the spring the wild plants are first up, and the attack is largely 
concentrated on them, so that when the beans come up they are not 
immediately attacked. However, in a few weeks the insect spreads 
to the beans, thereafter increasing in numbers until in the late sum- 
mer and fall much injury is done. When snap beans are infested 
the adults first attack the leaves, and while feeding lay countless eggs 
in the tissue. The larvae on hatching begin to feed, and gradually 
the green coloring matter is entirely removed from the underside of 
the leaf. This becomes white and covered with the black spots of 
excrement. The infestation then spreads to the surface and to other 
parts of the plant. As the feeding goes on the leaves lose all color, 
become white, or dry up and turn brown and drop off. As the infes- 
tation increases, the stems and pods themselves are also attacked and 
ruined. A badly infested field appears as if scorched by fire. The 
lima bean and pink bean suffer in the same way. The blackeye cow- 
peas this past season were almost immune from the attack of this 
insect, even in fields in which the pink beans and spiny lettuce were 
very badly infested. 
