90 MISSOURI BOTANICAL GARDEN BULLETIN 
in color, measuring one-seventh of an inch in length. From 
= pupa develops the winged insect, completing the life 
cycle. 
Detection and Eradication—When importations arrive 
from South America it is almost impossible to find any 
traces of the pests except in the developed pseudo-bulbs, from 
which they have made their escape. However, it is advis- 
able to take the precaution of fumigating with hydrocyanic 
gas, as there is always the possibility of the winged insect 
having developed in transit. After the plants have become 
established and the dormant eyes begin to show activity, 
daily examination is essential, since this is the critical period 
when the larvae are feeding and may be detected. The first 
fumigation should not be relied upon as final, because if 
the young growths do contain eggs, it is not possible to 
reach and destroy them with gas. 
The presence of the insect in the young growths may be 
detected by their abnormal shape. ‘Under normal condi- 
tions they are strap-shaped and slightly rounded at the base. 
If the growths are infested with the larvae or pupae, they 
will appear unnaturally large, rounded and gradually taper- 
ing to a point, especially when they are about two to three _ 
inches in height. If these characteristics are noticed, there 
should not be the slightest hesitancy in cutting the growths 
off close to the parent pseudo-bulb and burning them, be- 
cause each contains eight to ten small black pupae which will 
eventually develop into adult or winged insects. Com- 
mercial growers would no doubt hesitate to cut these young 
shoots because of losing the blooms. However, if they are 
left, the growths are finally too crippled to develop flowers 
and an opportunity is given the insect to reproduce. The 
parent pseudo-bulb is always supplied with dormant eyes or 
growths which will soon develop after the infested growth 
has been removed, and will produce flowers almost as fine 
as the lead, although the flowering period will naturally be 
a few weeks later. 
Cyanide Fumigation—Even if the orchid fly has been 
located during its early stages, there is still a possibility that 
some have been overlooked and have developed into winged 
insects. In any case it is advisable to fumigate with hydro- 
cyanie gas weekly until the pseudo-bulbs are well developed. 
This will certainly eradicate the pest in the final stage, pre- 
venting the possibility of reproduction. 
Careful preparations should be made for fumigating, 
evening being the best time for the work. The greenhouse 
and plants should be kept dry the entire preceding day, the 
