(_Tetranyehus telarius._)
The red spider is not correctly speaking an insect, though it is
commonly spoken of as such, neither is it a spider, as its name would
imply, but an acarus or mite. Whether its name is correct or not, it
is a most destructive and troublesome pest wherever it makes its
presence felt, it by no means confines itself to one or only a few
kinds of plants, as many insects do, but it is very indiscriminate in
its choice of food, and it attacks both plants grown under glass and
those in the open air. When these pests are present in large numbers,
the leaves on which they feed soon present a sickly yellow or scorched
appearance, for the supply of sap is drawn off by myriads of these
little mites, which congregate on the under sides of the leaves, where
they live in a very delicate web, which they spin, and multiply very
rapidly; this web and the excrement of the red spider soon choke up
the pores of the leaves, which, deprived of their proper amount of
sap, and unable to procure the carbon from the atmosphere which they
so much need, are soon in a sorry plight. However promiscuous these
mites may be in their choice of food plants--melons, cucumbers, kidney
beans, hops, vines, apple, pear, plum, peach trees, limes, roses,
laurustinus, cactuses, clover, ferns, orchids, and various stove and
greenhouse plants being their particular favorites--they are by no
means insensible to the difference between dryness and moisture. To
the latter they have a most decided objection, and it is only in warm
and dry situations that they give much trouble, and it is nearly
always in dry seasons that plants, etc., out of doors suffer most from
these pests. Fruit trees grown against walls are particularly liable
to be attacked, since from their position the air round them is
generally warm and dry, and the cracks and boles in the walls are
favorite places for the red spider to shelter in, so that extra care
should be taken to prevent them from being infested, this may best be
effected by syringing the trees well night and morning with plain
water, directing the water particularly to the under sides of the
leaves, so as, if possible, to wash off the spiders and their webs. If
the trees be already attacked, adding soft soap and sulphur to the
water will destroy them.
[Illustration: FIG. 1--Red Spider (magnified). A 1. Ditto
(natural size). 2. Underside of head. 3. Foot. 4. Spinneret.]
Sulphur is one of the most efficient agents known for killing them,
but it will not, however, mix properly with water in its ordinary
form, but should be teated according to the following recipe:
Boil together in four gallons of water 1 lb. of flowers of sulphur and
2 lb. of fresh lime, and add 1½ lb. of soft soap, and, before using, 3
gallons more of water, or mix 4 oz of sulphate of lime with half that
weight of soft soap, and, when well mixed, add 1 gallon of hot water.
Use when cool enough to bear your hand in it. Any insecticide
containing sulphur is useful. The walls should be well washed with
some insecticide of this kind. Old walls in which the pointing is bad
and the bricks full of nail holes, etc., are very difficult to keep
free from red spider. They should be painted over with a strong
solution of soot water mixed with clay to form a paint. To a gallon of
this paint add 1 lb. of flowers of sulphur and 2 oz of soft soap.
This mixture should be thoroughly rubbed with a brush into every crack
and crevice of the walls, and if applied regularly every year would
probably prevent the trees from being badly attacked. As the red
spider passes the winter under some shelter, frequently choosing
stones, rubbish, etc., near the roots of the trees, keeping the ground
near the trees clean and well cultivated will tend greatly to diminish
their numbers. In vineries one of the best ways of destroying these
creatures is to paint the hot water pipes with one part of fresh lime
and two parts of flowers of sulphur mixed into a paint. If a flue is
painted in this way, great care should be taken that the sulphur does
not burn, or much damage may be done, as the flues may become much
hotter than hot water pipes. During the earlier stages of growth keep
the atmosphere moist and impregnated with ammonia by a layer of fresh
stable litter, or by painting the hot water pipes with guano made into
a paint, as long as the air in the house is kept moist there is not
much danger of a bad attack. As soon as the leaves are off, the canes
should be dressed with the recipe already given for painting the
walls, and two inches or so of the surface soil removed and replaced
with fresh and all the wood and iron work of the house well scrubbed.
If carnations are attacked, tying up some flowers of sulphur in a
muslin bag and sulphuring the plants liberally, and washing them well
in three days' time has been recommended.
Tobacco water and tobacco smoke will also kill these pests, but as
neither tobacco nor sulphuring the hot water pipes can always be
resorted to with safety in houses, by far the better way is to keep a
sharp look out for this pest, and as soon as a plant is found to be
attacked to at once clean it with an insecticide which it is known the
plant will bear, and by this means prevent other plants from being
infested. These little mites breed with astonishing rapidity, so that
great care should be exercised in at once stopping an attack. A lady
friend of mine had some castor oil plants growing in pots in a window
which were badly attacked, and found that some lady-birds soon made
short work of the mites and cleared the plants. The red spider lays
its eggs among the threads of the web which it weaves over the under
sides of the leaves; the eggs are round and white; the young spiders
are hatched in about a week, and they very much resemble their parents
in general appearance, but they have only three pairs of legs instead
of four at first, and they do not acquire the fourth pair until they
have changed their skins several times; they are, of course, much
smaller in size, but are, however, in proportion just as destructive
as the older ones. They obtain the juices of the leaves by eating
through the skin with their mandibles, and then thrusting in their
probosces or suckers (Fig. 2), through which they draw out the juices.
These little creatures are so transparent, that it is very difficult
to make out all the details of their mouths accurately. The females
are very fertile, and breed with great rapidity under favorable
circumstances all the year round.
The red spiders, as I have already stated, are not real spiders, but
belong to the family Acarina or mites, a family included in the same
class (the arachnida) as the true spiders, from which they may be
easily distinguished by the want of any apparent division between the
head and thorax and body; in the true spiders the head and thorax are
united together and form one piece, to which the body is joined by a
slender waist. The arachnidæ are followed by the myriapoda
(centipedes, etc.), and these by the insectiæ or true insects. The red
spiders belong to the kind of mites called spinning mites, to
distinguish them from those which do not form a web of any kind. It is
not quite certain at present whether there is only one or more species
of red spider; but this is immaterial to the horticulturist, as their
habits and the means for their destruction are the same. The red
spider (Tetranychus telarius--Fig. 1) is very minute, not measuring
more than the sixtieth of an inch in length when full grown; their
color is very variable, some individuals being nearly white, others
greenish, or various shades of orange, and red. This variation in
color probably depends somewhat on their age or food--the red ones are
generally supposed to be the most mature. The head is furnished with a
pair of pointed mandibles, between which is a pointed beak or sucker
(Fig. 2). The legs are eight in number; the two front pairs project
forward and the other two backward; they are covered with long stiff
hairs; the extremities of the feet are provided with long bent hairs,
which are each terminated by a knob. The legs and feet appear to be
only used in drawing out the threads and weaving the web. The thread
is secreted by a nipple or spinneret (Fig. 4) situated near the apex
of the body on the under side. The upper surface of the body is
sparingly covered with long stiff hairs.--_G.S.S., in The Garden._
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