136 
tendent of Lincoln Park, Chicago, and the adult insect bred from 
them by Prof. F. M. Webster, at that time an assistant of the 
office. 
Buds infested by the orchid Isosoma become badly swollen at 
the point of attachment, and if examined will be found to contain 
a white maggot-like larva—perhaps more than one. The char¬ 
acteristic enlargement of an infested bud, and the cavity within, 
are well shown in the accompanying illustration (Fig 50). After 
the adult (Fig. 51) escapes, the basal bud-scale changes to a red¬ 
dish color, and later becomes blackish. An infested pseudo-bulb 
never produces a flower. Furthermore, a plant badly infested 
loses its vigor, and if the attacks are not checked it will die in 
a year or two. We have found only orchids of the genus Cattlcya 
infested by this insect, and it apparently has a decided preference 
for species known to florists as C. gigas and C. labiata. 
The adult (Fig. 51) is a small, clear-winged, wasp-like insect, 
with the head and thorax dull black and the abdomen shining 
black. The female is about 1/7 of an inch in length—the male 
is somewhat shorter—and has a long, slender ovipositor, which 
is ordinarily concealed in a sheath on the under side of the ab¬ 
domen. By means of this long ovipositor the egg is placed in 
the center of the small flower-bulb, near the base, and the small 
larva hatching later, feeds on the tissues, and burrows out a small 
cavity in the center, the embryo flower-bud within being thus 
destroyed. Altho the female usually inserts several eggs in a bulb, 
each one is deposited singly. The small, individual cavities, as 
they are enlarged bv the larvae, merge in a single larger burrow. 
When full grown the larva changes to a whitish pupa and later 
to the adult insect, which in due time escapes from the bulb. Ac¬ 
cording to observations made by Decaux in greenhouses in France, 
the total life cycle requires at least 50 or 60 days.* 
The following interesting particulars are taken from unpub¬ 
lished notes of Professor Webster. 
Buds were received April 15, 1904, at which time one of the 
blossom-buds was badly swollen at the base, indicating the pres¬ 
ence of the larva. The bud was growing somewhat pointed, with 
the point rather hook-shaped and turned upward. “The infested 
bud continued to grow but retained the original shape [above 
described], nothing developing till May 28, when winged adults 
of this species of Isosoma [/. orchidearum ], of both sexes, ap¬ 
peared in the cage. There were no visible holes in the bud where¬ 
by the insects escaped from it, and they must have issued from 
*Note pour servir a l’fitnde de la Mouche des Orchidees, Isosoma orchid- 
ccarum. (Westwood). Le Naturaliste, Ser. 2, No. 255* Oct. 15. tSo/, pp. 233 " 
237. 7 figures. 
