14  ~— BULLETIN 833, U. S. DEPARTMENT OF AGRICULTURE. 
larvee live within the galls alongside the maggots of the gallfly, which they gradually 
consume. They remain within the galls until mature, when they emerge through small 
circular holes. This species is the most abundant during the summer months and all 
of the adults were reared during August, September, and October. In not afew cases 
as high as 80 per cent to 90 per cent of the maggots were destroyed. 
Tetrastichus sp. The generic determination of this insect was made by Mr. Harry S. 
Smith, superintendent of the State insectary, Sacramento, Calif. It is also a small 
black parasite, somewhat larger than the former and easily distinguished irom it by 
the four-jointed tarsi and other characters. 
EXPERIMENTS IN CONTROL. 
At the outset it must be borne in mind that it is very important 
that control measures should be closely related to the propagation of 
the stock, and moreover from the practical and economical point of 
view these steps should be undertaken at a period in the propagation 
when the plants can be severely cut back, allowing sufficient time to 
overcome any injury which may result from such treatment. Inas- 
much as cuttings are propagated from the stock plants of the previous 
season, it is evident that the logical time to eradicate an infestation 
of long standing is immediately after the flowers have been removed. 
Naturally such precautions as would absolutely safeguard the grower 
against further spread and increase would have to be inaugurated. 
An experiment conducted in one of the commercial greenhouses in 
the District of Columbia in which the plants had been heavily infested 
the previous season was carried out asfollows: These heavily infested 
stock plants were heeled in and pruned back, and the entire portion 
above ground was thoroughly dusted with a mixture of equal! parts 
of tobacco dust and air-slaked lime as often as the new growth 
appeared. As a result of such treatment the new growth was kept 
practically clean from further infestation and the plants at the same 
time showed a stimulated growth. The checks which were run simul- 
taneously had all the new growth badly infested. 
Occasionally it may happen that a grower’s previous season’s stock 
was clean and new material or varieties are being received in the form 
of cuttings or young plants from localities where the insect is known 
toexist. There is a possibility of introducing the midge on such stock 
even though no definite signs of the insect are visible. In the spring 
when cuttings and young plants are being exchanged, an infestation, 
especially in the egg or very young larval stage, will defy even the 
most careful and zealous inspectors. Interception made of plants 
harboring the eggs only can easily be overlooked by virtue of their 
concealed location in the still unfurled leaf bud. 
A precautionary treatment should be given at the time when the 
plants or cuttings are taken or received and would prove of inesti- 
mable value in killing the eggs and immature stages. 
The question of controlling an infestation already in the well- 
developed gall stage as well as the adult stage must also be con- 
