148 THE ORCHID REVIEW. 
weak tobacco water, and, judging from the cleanness and vigour of the 
plants so treated I am practising his method, and believe if I had adopted 
it earlier I might have had better success in the destruction of the pests. 
T. W. RUSSELL. 
Kelvinside, Glasgow. 
It is evident from the remarks at pages 44, 87, and 10g that our know- 
ledge of this troublesome pest is far from complete, and one can hardly 
avoid a suspicion that more than one insect is concerned, especially as it is 
first said to have been found on a Saccolabium. The following is briefly 
its history, so far as we can discover :—In 1869 a note was given by Pro- 
fessor Westwood of some white fleshy larvee, with chestnut-coloured shining 
heads, found by Mr. Bateman feeding in the substance of the leaves of an 
Orchid, said to be a Saccolabium. Professor Westwood extracted a male 
and female pupa, which he referred to the Chalcidide, and named the 
insect Isosoma Orchidearum, remarking that it was probably a vegetable 
feeder, though other members of the group were insectivorous, or parasitic 
on other insects. He added, however, that little was known of the history 
of the insects which attack exotic Orchids, as collectors only selected 
healthy specimens. (Gard. Chron., 1869, pp. 196, 252, 1230, with fig.) 
For a long period very little farther seems to have been discovered, though & 
there was some discussion as to whether the Isosoma was the cause of the 
mischief, or only a parasite on some other insect, Mr. McLachlan taking 4 
the view that it was parasitic on some Cecidomyia, which was the real ; 
cause of the mischief, and stating that he had bred both insects from galls 
on Cattleya roots. It is now known, however, that the larve of the 
Isosoma, which are white, are true vegetable feeders. Cecidomyia, on the 
other hand, has orange-coloured larve. In June, 1878, a gall was found 
on the roots of a Dendrobium in the collection of G. E. Cox, Esqs L 
Leyton, and inside this was found the yellow larve of some Cecidomyia. 
In 1885 a paper appeared, entitled “ Galls on the roots of Orchids” (Gard. 
Chron., 1885, xxiv., p. 84), when both the galls of Cattleya (fig. 19) and 
Dendrobium (fig. 20) were shown. In 1890 all the figures were 1 
Produced (/. c., 1890, viii., p. 505). Shortly afterwards Mr. C. V- Riley 
confirmed Professor Westwood’s contention that the larve of Isosoma were 
phytophagous, as he had seen them feeding, and had bred both sexes of the 
insect (I. c., 1891, ix., P- 597). If these are identical with those originally 
found on Saccabium, it is, to say the least, very curious, and suggests = 
question whether the Orchid on which the insect was originally found was 
really a Saccolabium. Next to knowing how to combat the insect whet 
found, it is important to know with what particular species of Orchid it 15 
imported, so as to be on the alert. It is pretty clear that recent attacks can 
