Unfortunately for the well-being of collections, dried insects are
liable to the attacks of various museum pests, the most troublesome of
which are themselves insects, but altogether out of their proper place
and role in the general collection. Unless constant precautions are
taken, the collector will discover after a few months that instead of
the rare specimens with the preparations of which he has taken no little
pains there remains only a series of fragmentary specimens, which a few
years' neglect will reduce to little more than a mass of dust or powder.
The price, then, of a good collection is eternal vigilance. Most
insects, when exposed for any length of time to strong light, fade or
lose color, and the only way to prevent such achromatism is to exclude
the light.
Insect pests affecting collections include Psocidae, Mites, Tineidae,
Coleoptera of the families Ptinidae and Dermestidae, these last being the
most injurious.
[Illustration: FIG. 121.--_Tineola biselliella_: _a_, adult; _b_, larva;
_c_, cocoon and empty pupa--skin enlarged.]
The Psocidae--degraded wingless insects already referred to in the
classification (p. 24)--will find their way into the tightest boxes, but
ordinarily do little if any damage, except in the case of delicate
insects, such as Ephemerids, Microlepidoptera, and Microdiptera. The
common forms found in collections are _Atropos divinatorius_ and
_Clothilla pulsatoria_. Mites or Acari are rarely troublesome in
collections, though Dr. H. A. Hagen reports having found a species
(probably of Tyroglyphus) with imported insects, and considers them as
liable to become dangerous enemies. Tineid larvae are rarely found in
collections, and only affect the larger moths. They are not easily
discovered, since they make no dust, as do most other pests. Some
persons have been considerably annoyed by one of the common clothes
moths, _Tineola biselliella_ (Fig. 121). Dr. Hagen found that it
attacked freshly collected or newly spread insects, where the
spreading-boards were left uncovered, but Mr. F. M. Webster has found it
injurious to the general collections at Columbus, Ohio.
Of beetles, the Ptinidae are sometimes found in collections but are not
common. Two species are known to attack entomological specimens, namely,
_Ptinus fur_, which is quite rare, in this country, but much more
abundant in Europe, and _Tribolium ferrugineum_, a cosmopolitan species
which, however, has several times been associated in injurious numbers
with large collections of insects imported from the East Indies.
But by far the most dangerous enemies of insect collections are the
larvae of some half dozen or more species of Dermestidae belonging to the
genera Anthrenus, Attagenus, Trogoderma, and Dermestes. Of these
_Anthrenus varius_ is the more common pest, in museums, especially in
the North and East. In the South and West _Trogoderma tarsale_ and _T.
ornatum_ (?) replace Anthrenus. The European species _Anthrenus
musaeorum_, is, on the authority of Hagen, rare in this country, and
probably occurs chiefly in collections of imported insects. It is the
common injurious species of Europe. _Anthrenus scrophulariae_ (see Fig.
67) occurs also in collections, Dr. Hagen stating that he has found it
nearly as common as _A. varius_, and certainly more dangerous. In my own
experience it is rarely found in insect collections. Two species of
Attagenus (_A. pellio_ and _A. megatoma_) have also been found in
collections. _A. megatoma_ has been found by Dr. Hagen to do not a
little damage to insect collections in Cambridge, as well as to equal if
not exceed the Carpet Beetle in its disastrous attacks upon carpets and
household furniture. The other species, _A. pellio_, is rarely found in
this country, but is much more common and obnoxious in Europe than _A.
megatoma_. _Dermestes lardarius_ is sometimes found in collections, and
is attracted by the presence of animal matter such as skins, etc. The
two particularly destructive pests, as pointed out, are _Anthrenus
varius_ and _Trogoderma tarsale_. These species, together with most of
the others, have no definite breeding period, but, in the uniform
temperature of the laboratory or museum, breed all the year round and
present no definite broods. It is the experience at the Museum that the
boxes on the lower tier of shelves are very much more subject to attack
than those on the upper tiers, from which it would seem that the parent
beetle deposits her eggs outside the boxes on the floor of the cases and
that the young larvae work their way into the smallest crevices. The
danger of infection by these pests is greater in warm climates like that
of Washington than in regions further north, as the warm season begins
earlier, lasts longer, and furnishes better conditions for breeding and
multiplication.
[Illustration: Fig. 122.--A naphthaline cone.]
REMEDIES.--The following remedies and preventives will prove efficient
in checking or preventing the work of these pests.
_Naphthaline._--Where tight boxes are employed little fear of the work
of these destructive agents need arise, especially if the boxes are kept
supplied with repellent naphthaline cones. These are hard cones of
naphthaline, mounted on pins for convenient placing in the boxes (see
Fig. 122), and may be obtained of dealers in entomological supplies.
Naphthaline cones act as repellents to these insects and also to some
extent retard the development of the larvae in all stages and
particularly of the eggs.
Mr. Schwarz states (_Proc. Ent. Soc. of Washington_, Vol. I, page 63)
that in place of these cones a form of naphthaline may be used which is
known in commerce as "white carbon," and is put up in the form of small
square rods for use in intensifying the flames of gaslight. The material
is very cheap, costing only 8 cents per pound wholesale, and may be
broken up into small pieces, wrapped in paper, and pinned. The use of
naphthaline cones is not advisable in boxes containing delicate
specimens, as it leaves a deposit which dulls the colors and encourages
greasing. The deliquescence of the naphthaline cones produces a
blackish, oily residuum which will soil the lining of the box, and it is
always advisable either to pin a piece of blotting paper beneath the
cone or to wrap this in paper.
Constant watchfulness is necessary to see that the eggs which have been
deposited and checked in development by the application of this
insecticide do not ultimately hatch and start a new generation in the
insect box.
_Bisulphide of Carbon._--If the collection is found to be infested with
insect pests, it may be renovated by pouring a little bisulphide of
carbon into the boxes and closing them at once. This substance
evaporates rapidly and will destroy all insect life, and does not injure
specimens or pins nor stain the boxes. If infested specimens are
received, these should be inclosed in a tight box and treated with
bisulphide of carbon before being added to the general collection, and
it is always well for those who are receiving pinned specimens by
exchange or otherwise to keep a quarantine box of this kind on hand.
_Mercury Pellets._--The use of mercury pellets is recommended to free
boxes from Mites, Psoci, etc., and also to collect any particles of dust
which may gain entrance. A few small pellets of mercury, placed free in
the bottom of the horizontal box will, by the movement of the box, be
caused to roll to and fro and accomplish the desired end.
_Carbolic Acid._--Mr. A. T. Marshall (_Entomologist's Monthly Magazine_,
Dec., 1873, p. 176) records that he washes the paper of his boxes with
the common disinfecting solution of carbolic acid in two-thirds water,
which dries without staining and protects the specimens from Psoci.
_A Means of preserving Insects in dry hot Countries._--In the "_Horae
Societatis Entomologicae Rossicae_," XXIV, pp. 233, 234 (1889), M. A.
Wilkins, writing from Tachkent in Turkestan, alludes to the inefficiency
of ordinary preservatives in Central Asia, on account of their rapid
volatilization through the hot dry air, so that if a collection be
neglected for only two or three months _Anthreni_ are sure to be found
in the boxes. He has hit upon a plan which he finds effective, and at
the same time very simple. He employs India-rubber bands about 11/2 inches
in width and less than the length of the boxes to which they are to be
applied. These bands are stretched over the opening line of the boxes,
and effectually prevent the entrance of the most minute destroyers.
Possibly a similar plan might be adopted in other countries with a like
climate. At any rate, the method has the merit of extreme simplicity.
(The _Ent. Mo. Mag._, Apr., 1891, p. 107.)