26 THE BEAN THBIPS. 
The molting from larva to prepupa under laboratory conditions has 
been observed many times. On April 10, 1911, a mature larva was 
observed to begin the process at 4.05 in the afternoon. After remain- 
ing motionless for some time it arched its body, and shortly after 
the skin split down the head behind the antennse. The head grad- 
ually forced its way out of the opening, then the body followed, the 
old skin being slipped off behind. This molting was completed at 
4.21 p. m. 
HABITS OF THE PREPUPA AND PUPA. 
The prepupa? of this insect are found in company with the pupa? 
and full-grown larva? in small social colonies. These hold the 
antenna? out in front of the body and move about to some extent. 
The pupa?, however, carry the antenna? folded back on the head and 
thorax and remain motionless unless disturbed or exposed to the 
light, in which cases they will slowly crawl away. TVlien com- 
pelled to pupate in closed vials the prepupa? and pupa? occur in 
large numbers closely packed together along the edge of the vial 
and the cotton plug or buried in the cotton itself. In nature it has 
quite different habits. While the greenhouse thrips under natural 
conditions pupates on the leaf of the food plant in among the feeding 
larvae, with the bean thrips this seldom takes place, and during the 
two years this species has been under observation by the writer only 
three pupa? have been found on the plants infested by hundreds of 
thousands of larva?. In one case a pupa was found under the web of 
the red spider near the midrib of a leaf of spiny lettuce ; in another, 
one was found under a web of red spider on a leaf of the wild tobacco 
flower; and the third was found in a curled-up lettuce leaf. 
December IT, 1910, a quantity of the dead leaves of wild helio- 
trope Avere collected on the ground under infested plants. Prolonged 
sifting revealed the presence of a single pupa. In 1911, the prepupa? 
and pupa? were found by Mr. John E. Graf and the writer to be 
very abundant in infested bean fields under clods or lumps of dry 
earth and in cracks or holes in the lumps. Upon exposure to the 
light these at once began to move away in search of darkness. 
Mr. Wildermuth also found the pupa? of this insect underground. 
He wrote in his notes on September 23 : 
While searching by aid of a binocular for pupae, I found one pupa, one 
prepupa, and two (mature) larva? just at the crown of the plant and beneath 
the soil; one pupa about one-fourth inch below the surface of the soil in an 
oval cavity about three times as long as the pupa itself : one prepupa between a 
dead leaf and the soil. Never have I found a pupa above the surface of the 
ground, on the leaves of the plant, or between the sheath leaves and the stem, 
as frequently occurs in confinement. 
The molting of the prepupa to the pupal stage is very similar to 
that described for the change of the larva to the prepupa. It takes 
