808 A. FE. Verrill—The Bermuda Islands. 391 
plants, or on fruit, or even on cuttings of vines and trees. It is well 
known that some of these have been particularly destructive to the 
orange and lemon trees in Bermuda (see pp. 526, 635), and doubtless 
also to other fruit trees, as the peach, fig, pomegranate, avocado 
: x 
pear, etc. 
The vast economic importance of the Scale-insects, as affecting 
* The killing of these very destructive insect pests is absolutely necessary in 
cultivating fruit trees successfully, according to modern methods. All repu- 
table dealers in nursery stock in the United States now give written guarantees 
that all stock sold is free from such insects, or that it has been properly fumi- 
gated. Local laws should prohibit the importation of all nursery stock without 
such a certificate, or else should provide for careful inspection before eutry. 
The use of hydrocyanic-acid gas for disinfecting nursery stock, as well as 
growing trees of large size, is now extensively employed in the United States, 
with excellent results. It is equally applicable for killing all kinds of insects in 
conservatories, unoccupied dwellings, storehouses, ete. 
The proportion of potassium cyanide required for very thorough fumigation is 
1 oz. av. for every 100 cubic feet of space. For every ounce of cyanide 1 fluid 
oz. of sulphuric acid is required; it is to be diluted with 2 or 3 parts of water, 
before using. The cyanide, done up in thin paper packages, each of the proper 
quantity for a tent or room, is dropped into the dilute acid contained in suitable 
porcelain or stone-ware receptacles (earthenware wash-bowls or pitchers do 
very well) large enough to avoid overflow by the foaming and then the doors to 
rooms or tents are quickly closed, and kept closed for an hour or more, if pos- 
sible, though half an hour is often effectual. Rooms should be thoroughly aired 
for several hours before being again occupied, for the gas is very deadly. All 
windows and cracks should be tightly closed before fumigating. A small wire 
or string may be used to suspend the packages of cyanide over the acid, so that 
these can be dropped into it from outside the closed doors or windows, by 
releasing or cutting the strings, thus avoiding the fumes. The receptacles for 
the acid should be placed on thick papers, boards, or some other material to 
protect floors from the spatterings of the acid, when used in dwellings. The 
tents used for covering fruit trees for fumigation can be made of thin drilling 
rendered nearly air-tight by some suitable flexible varnish, such as boiled lin- 
seed oil, or by a mixture of paraffine and naphtha, used as a varnish. Smail tents 
for young trees can be cheaply supported by a light frame made of one or more 
barrel hoops which can be made to fold up if desirable ; for small trees some 
have used light octagonal frames covered with strong paper, and having a coni- 
cal hood. If enclosures are not very tight, more cyanide and acid must be used. 
Kerosene emulsion sprayed over the trees, or even applied to the trunk and 
branches with a brush, is also very effective. One pound of soap is dissolved in 
1 gallon of hot water ; this after cooling to be mixed with 2 gallons of kerosene ; 
the whole to be churned together, by means of a syringe or force pump, till it 
forms a creamy emulsion. This is diluted with 8 to 10 parts of water when 
used for scales. This emulsion is also effectual against all other insects on 
trees when more diluted, even with 12 to 15 parts of water. 
