[The Haversack.]—In order that the above-mentioned instruments and the various bottles, vials, and boxes which are needed for the preservation of specimens may most conveniently and with the least impediment to the collector be carried along on excursions, a haversack is indispensable. This is made either of leather or, still better, of some waterproof cloth, and should contain various compartments of different sizes; one for stowing away the nets, the sieve, and the larger instruments, and several smaller ones for boxes and vials—the whole so arranged that each desired object can readily be taken out and that nothing will drop out and get lost. The haversack is slung across the shoulders by means of a leather strap, and a full field outfit need not be very heavy nor seriously interfere with free bodily movements.
Many of the smaller objects are most conveniently carried in the pockets of the coat, which acquires, therefore, some importance to the collector. The coat should be of some durable stuff and provided with many pockets, so arranged that in stooping nothing falls out of them.
[The Lens and Microscope.]—In the examination of the minuter forms of insect life the naked eye is not sufficient, and a hand-lens, or, for more delicate work, the compound microscope will be found necessary. I had, in my early experience, some difficulty in getting a satisfactory hand-lens, and the use of a poor hand-lens in time injures the eyesight, as I know by a year's rather disagreeable experience. For a hand-lens the achromatic lenses formerly manufactured by A. K. Eaton, of Brooklyn, N. Y., and now made by John Green, 35 Liverpool street, East Boston, Mass., are most excellent in workmanship and are satisfactory in every respect. A very good lens can also be purchased of any of the leading manufacturers of microscopical apparatus in this country. The kind of compound microscope to be purchased will depend upon the nature of the work of the investigator. Very serviceable instruments are made by J. W. Queen & Co., Philadelphia, Pa., and by the Bausch & Lomb Optical Company, of Rochester, N. Y., and others. The German microscopes are in many respects superior to those of American make, and if one has sufficient means, I would recommend the purchase of one of the better instruments of Zeiss's manufacture, which may be obtained either direct from the manufacturers or through Queen & Co., or from the Boston Educational Supply Company. Microscopic material, including slides, cover glasses, instruments for mounting, mounting media, staining fluids, etc., may be obtained of either of the firms named above.
Having thus indicated somewhat fully the general methods of collecting, and the paraphernalia most desirable in collecting, it will be well to go still further into detail, and in connection with the different orders give some more specific information that will be valuable as a guide not only to the general collector, but to the specialist.
[COLLECTING HYMENOPTERA.]
The insects of this order, including Bees, Wasps, Ants, Ichneumon-flies, Gall-flies, Saw-flies, and allied insects have always been of unusual interest both to entomologists and non-entomologists on account of their diversified and peculiar habits. In abundance of species they exceed perhaps even the Coleoptera. In general they are day fliers and always to be found in abundance on bright days about flowers. The best season for collecting is in early spring, on the bloom of the Willow, Alder, and other trees. They may also be found at any season of the year, but the males of many species are only to be taken in fall. In this order, species of many groups can be most easily obtained by breeding. This includes the gall-making family, Cynipidæ, and the parasitic families Chalcididæ, Proctotrypidæ, Ichneumonidæ and Braconidæ. The Chrysididæ and certain other less important families are also parasitic, but are more easily obtained by general collecting. The implements necessary for collecting Hymenoptera are the sweeping-net and the beating-net. Many rare forms of the smaller parasitic families may be obtained by sweeping the grass and foliage of all sorts. The Proctotrypidæ may be collected in quantity by sifting leaves and rubbish collected in the woods. Mr. William H. Ashmead, who has made an especial study of this group, finds winter sifting profitable. Dried leaves and rubbish are sifted, the finer portion being retained and transferred to a bag. When a sufficient quantity is collected it is removed to a warm room. Many hibernating species are taken in this way, and, revived by the warmth, are easily noticed when the material is spread on white paper.
Fig. 60.—A Saw-fly (Nematus ventralis). a, a, a, young larvæ; b, full-grown larva; c, cocoon; d, adult; all slightly enlarged.
On account of the interest attaching to a knowledge of the various hosts of parasitic insects the collector should always aim to obtain the latter by breeding as much as possible. This can easily be done by keeping a lookout for larvæ of all sorts which give evidence of being parasitized. The larvæ of Lepidoptera found late in the fall are very apt to be parasitized, and should be collected and kept over the winter. The parasites will emerge throughout the winter season and in the early spring. Such larvæ will be found on the trunks of trees, in the crevices of the bark, and the cocoons of parasites will also be found in similar situations.
The Tenthredinidæ (Saw-flies) are not so often found about flowers but usually remain in the vicinity of the food-plant of the larva, and may many of them be collected by sweeping. The larvæ of this family are in many cases difficult to breed, as most of them are single-brooded, and it becomes necessary to carry the larvæ over the winter.