20 THE BEAN THEIPS. 
than those observed by the writer. This may have been due to the 
higher temperature of the Imperial Valley and vicinity, where his 
observations were made. Mr. Wildermuth noted adults in copula- 
tion the day that they emerged, and oviposition on the following- 
date. He also observed this species to oviposit during the entire day, 
whereas the writer never observed it to oviposit except in the after- 
noon or night. 
PROPORTION OF THE SEXES. 
The bean thrips was under the observation of the writer for a 
period of more than two years, during which time it had been ob- 
served in the field at all times of the year. In all observations made 
during the investigation of this insect the males and females were 
collected together and copulation was observed from early in Febru- 
ary until reproduction ceased late in the fall. Apparently the 
females outnumber the males, but this may be due to the fact that 
the females are not quite so active as the males, and are not dis- 
turbed on the plants when examined. On June 9, 1911, out of IT 
specimens reared in the laboratory 9 were females and 8 males. July 
17, 1911, the writer examined another series of live adults that were 
reared in the laboratory. Out of 10G, 80 were females and 2G males. 
A third series of reared adults was examined October 1G, 1911, and 
out of 44 adults 32 were females and 12 males. Apparently the per- 
centage of females is too high and does not indicate the exact rela- 
tion between the sexes. 
KINDS OF REPRODUCTION. 
In all observations made on this topic reproduction has been 
bisexual, and in view of the fact that males were observed at all 
times and copulation also occurred at all times in the year when 
this insect was active, this would seem to be the usual method. How- 
ever, although the few experiments made to determine whether 
parthenogenesis occurred gave negative results, in view of the pre- 
ponderance of females during certain parts of the season it is quite 
probable that asexual reproduction may occur. It would seem that 
this method would occur under certain conditions, especially in 
view of the fact that the greenhouse thrips (Heliotkrips hmmorrhoi- 
dalis) 1 reproduces, so far as we know, asexually only, the male hav- 
ing- never been discovered. 
FEEDING HABITS. 
Both the adult and larva of this thrips injure the host by feeding 
on the foliage. As in the case of the greenhouse thrips, the lower 
i " The Greenhouse Thrips," Bui. 64, Bur. Ent., U. S. Dept. Agr. 
