For several years past, I have devoted a portion of my leisure time to
the arrangement of the collection of Arachnidæ of the Natural History
Museum of the University of Gand. This collection, which is partially
a result of my own captures, is quite a large one, for a university
museum, since it comprises more than six hundred European and foreign
specimens. Each group of individuals of the small forms and each
individual of the large forms is contained in a bottle of alcohol
closed with a ground glass stopper, and, whenever possible, the
specimens have been spread out and fixed upon strips of glass.
The loss of alcohol through evaporation is almost entirely prevented
by paraffining the stoppers and tying a piece of bladder over them.
Properly labeled, the series has a very satisfactory aspect, and is
easily consulted for study. The reader, however, will readily
understand how much time and patience such work requires, and can
easily imagine how great an amount of space the collection occupies,
it being at least twenty times greater than that that would be taken
up by a collection of an equal number of insects mounted in the
ordinary way on pins and kept in boxes.
These inconveniences led me to endeavor to find out whether there was
not some way of preserving spiders, properly so called, in a dry
state, and without distortion or notable modification of their colors.
Experience long ago taught me that pure and simple desiccation, after
a more or less prolonged immersion in alcohol, gives passable results
only with scorpions, galeodes, phrynes, and mygales, and consequently
with arachnides having thick integuments, while it is entirely
unsuccessful with most of the spiders. The abdomen of these shrivels,
the characteristic colors disappear in great part, and the animals
become unrecognizable.
Something else was therefore necessary, and I thought of carbolated
glycerine. My process, which I have tried only upon the common species
of the country--_Tegenaria domestica_, _Epeira cucurbitina_, _Zilla
inclinata_, etc., having furnished me with preparations that were
generally satisfactory. I think I shall be doing collectors a service
by publishing it in the _Naturaliste_.
The specimens should first be deprived of moisture, that is to say,
they should be allowed to remain eight or ten days in succession in 50
per cent. alcohol and in pure commercial alcohol. Absolute alcohol is
not necessary.
After being taken from the alcohol, and allowed to drain, the
specimens are immersed in a mixture compound of
Pure glycerine 2 volumes,
Pure carbolic acid in crystals 1 volume.
In this they ought to remain at least a week, but there will be no
harm if they are left therein indefinitely, so that the collections of
summer may be mounted during winter evenings.
What follows is a little more delicate, although very easy. After
being removed from the carbolated glycerine, the spiders are placed
upon several folds of white filtering paper, and are changed from time
to time until the greatest part of the liquid has been absorbed. An
insect pin is then passed through the cephalothorax of each individual
and is inserted in the support upon which the final desiccation is to
take place. This support consists of a piece of sheet cork tacked or
glued at the edges to a piece of wood at least one inch in thickness.
Upon the cork are placed four or five folds of filtering paper, so
that the ventral surface of the pinned spider is in contact with this
absorbing surface. For the rest, the legs, palpi, spinnerets, etc.,
are spread out by means of fine pins, precisely as would be done in
the case of coleoptera.
[Illustration: SETTING BOARD FOR SPIDERS.