INSECTS AND OTHER ANIMAL Pessts INJURIOUS TO FIELD BEANS 959 
In 1919 notes were taken on the period of incubation of 28 eggs on moist 
earth. The average for these was 2.8 days, with a range from one to 
five days. Four eggs kept on dry blotting-paper in a petri dish required 
between three and four days. One egg, deposited on June 4, did not hatch 
until June 17, but this is the only instance of so long a period of incubation. 
Place of oviposition 
The insect is strongly attracted to moist and decaying material as a 
place for oviposition, but under some conditions the flies will place their 
eggs on dry material, as the following experiment shows. On June 4, 1919, 
many flies, taken by sweeping, were placed in a cage with a flower-pot 
containing dry bean stems and dry soil. This pot was kept dry until the 
flies died, after which it was moistened in order to see whether a new lot 
of flies would develop. On July 3 one fly was found in the cage, and on 
July 8 two more were found. In another cage the same conditions pre- 
vailed except that the jar was moist during the entire experiment. Four 
flies were found in this cage on July 3, and eight more on July 8. 
In the field, eggs have been found around decaying bean pods and vines 
and around rotting cabbage. The writer has spent a great deal of time 
in looking for eggs on freshly plowed ground where mature flies were seen 
in large numbers, but has succeeded in finding only a few in such locations. 
Two eggs were found on newly turned soil and one was discovered in a 
‘erevice in a recently disked field. Egg-laying was induced by throwing 
water on the parched and cracking ground near the laboratory at a time 
when the flies were numerous. Eight eggs were found on top of the ground 
in one of these spots within two hours after it was thus moistened, and, in 
all, about one hundred eggs were obtained in this way. 
Whelan (1916) says that the maggots of H. cilicrura are sometimes found 
in fresh manure. The writer, however, has not seen the larvae in manure, 
nor has he been able to bring about oviposition on manure. On June 5, 
1919, flower-pots containing fresh cow, horse, hog, and hen manure were 
placed in a cage containing many adults of cilicrura that had been taken 
in the field. When these pots were examined later, no eggs could be found, 
and no flies ever emerged in the cage. On June 3, 1919, flies were placed 
in a large cage containing one flower-pot of manure of different kinds and 
another filled with decaying bean vines and grass sod. After the flies were 
all dead, the pot of manure was moved to another cage. No flies emerged 
from this pot. In the cage containing the pot with the decayed beans and 
grass sod, thirteen flies emerged. This apparently shows the insects’ 
preference for decaying beans and clover rather than for animal manure, 
as a place for oviposition. Many times fresh manure found in fields where 
the flies were abundant has been placed in cages, but no flies have ever 
emerged. Furthermore, the flies have not been found in abnormal num- 
bers around either manure piles or fresh manure dropped along the road. 
