Fig. 137.—Trombidium locustarum. a, mature larva when about to leave the wing of a locust; b, pupa; c, male adult when just from the pupa; d, female—the natural sizes indicated to the right; e, palpal claw and thumb; f, pedal claw; g, one of the barbed hairs; h, the striations on the larval skin.
Fig. 138.—The Six-spotted Mite of the Orange
(Tetranychus 6-maculatus): a, from above—enlarged;
b, tarsus; c, rostrum and palpus—still more enlarged;
d, tip of palpus—still more enlarged.
To this family also belong the common greenhouse mite, Tetranychus telarius, and also the Bryobia mite, B. pratensis, which of late years has attracted very considerable attention by its appearance in immense numbers about dwellings, coming from the adjoining fields of clover or grass. Generically allied to the greenhouse mite is the Six-spotted Mite of the Orange (T. 6-maculatus Riley), which is shown in the accompanying figure.
Spiders and mites thus collected may be transferred to alcohol. Dr. Marx, who has had a very considerable experience in the preservation of spiders, recommends the use of the following mixture: Glycerin and Wickersheim's fluid, 1½ ounces of each, and distilled water 3 ounces, the whole to be shaken and thoroughly mixed and added to 30 ounces of 95 per cent alcohol. Alcohol which has previously been used for preserving spiders, and which has therefore dissolved some of the fatty matters from the specimens, he prefers to pure alcohol, using with this, however, somewhat less of the distilled water. The liquid thus composed answers all demands and keeps the specimens flexible and preserves their coloring. Should the stopper become loose and the liquid evaporate, there is always sufficient liquid, water or glycerine, left in the vial to keep the specimens from drying and thus save them from destruction. Dr. Marx also prefers to use cork stoppers rather than the rubber stoppers recommended for other alcoholic material. His objection to the rubber stopper is that, in a collection in which the specimens are often used and the stoppers are frequently removed, he finds that small particles of the rubber stopper come off and settle upon the specimens as a white dust, which it is difficult to remove. This objection applies only to a poor quality of rubber, and in all other respects the rubber is much to be preferred. The colors of spiders are apt to fade somewhat if exposed to light, and the collection should therefore be kept in closed boxes or in the dark.
[COLLECTING MYRIAPODA.]
Centipedes and Millipedes are collected in the same manner as spiders. They live in damp places, under sticks and stones, and in decaying vegetation. They should be preserved in alcohol, and on account of their usually strong chitinous covering, precautions as to the strength of the alcohol are less necessary here than with softer-bodied specimens.
Fig. 139.—A Milliped. (Cambula annulata).