many of them are covered with fragile hairs and spines which are necessary for identification. No heavy or vigorous insect should be put into a killing jar with flies. For the best specimens, use several small killing vials, reserved for Diptera only. With husky species, such as Horse-flies and some Flower-flies, it is safe to fill the vial to capacity and leave it so all day. If it is as much as half full, the natural moisture of the specimens will keep the catch pliable until you return to your base, where you can empty the bottles and mount the specimens in one operation. The less often you handle Diptera, the more perfect they will be. In some groups of flies the male genitalia are used in making an identification and should be pulled out into plain sight at the time of pinning. If the catch consists of frail, pilose, or spiny species, not more than a dozen specimens should be put into a bottle at one time, and these should be removed within two or three hours at the most. Very particular dipterists may carry pins and cork-lined storage boxes with them, pinning their specimens in the field. Others pack theirs between layers of cotton in pill boxes. May-flies and some other ethereal creatures are on the borderline between the hard-bodied and the soft- bodied, and may be treated as either. Some students keep them in alcohol. Others pin them while fresh, or dry them unmounted and subsequently glue them to the sides of the pins without relaxing. Grasshoppers and katy-dids, dragon-flies and other thin skinned, bright colored, but heavy bodied insects present a problem. Due to their bulk they dry so slowly that the abdominal contents decay and stain the specimens. Methods of preventing this are varied. Forced drying is one. Evisceration and stuffing is another. Dragon-flies are sometimes placed alive in envelopes and starved to death, a process perhaps not so barbarous as it sounds, since it requires a few hours only. Alternatively, they can be collected into concen- trated alcohol. After two weeks in this bath they will be almost entirely de-hydrated and, when pinned, will dry immediately. Green pigmented species, mantises, katy-dids and others, keep their color best if killed and kept for several weeks in a 2% solution of formaldehyde before pinning. Stone-flies, lace-wings, and other large-winged, slight-bodied insects fit most readily into envelopes; bees and wasps, bugs, and other compact creatures, into cylinders or between layers of packing in a box. Directions for mounting large-winged species are given in Leaflet Number 5. SWEEPING The exceedingly rich but largely invisible fauna of thick foliage can be captured wholesale by swinging a net back and forth through herbage, or dragging it quickly through bushes and the leaves of trees. In order to withstand this violent treatment, a sweeping net is made of strong muslin with a heavy rim and short, thick handle. The catch obtained by this non-selective method consists of assorted botanical fragments, spiders young and old, beetles, leaf-hoppers, true-bugs, grasshoppers and oddments of other orders. In all probability, only a portion of this conglomeration will be of interest to any one collector, and you may have some trouble in selecting from the seething mass the specimens you want. You can, of course, just open the net and peer inside, trusting to luck and your own dexterity to sieze the valuable specimens while allow- ing the others to escape. You can dump the whole lot into the killing jar and cart it home to sort at leisure, thus needlessly slaying a great many harmless crea- tures. Or, you can shake the entire catch into the bottom of the net, secure it with a twist, and put net and all into a large killing bottle just long enough to anesthetize the animals. Then empty the net onto a cloth, or any clean surface, pick out the specimens you need, and drop them back into the killing jar or alcohol bottle as their struncture may indicate. The rejected remainder will soon revive, little the worse for the experience. Collectors who do a great deal of sweeping some- times use a separator to facilitate the sorting process. This separator is a box, large enough to contain several handfuls of leaves and having, near the top of one side, an opening at which a glass bottle may be at- tached. The top of the box is removable, so that it can be emptied easily. In the center of the lid is a hole, with stopper, through which the contents of the sweeping net are introduced. Most of the creatures inhabiting foliage are positively phototropic; that is, they seek the light. They have, moreover, a tendency to climb upward. When enclosed in a dark box they will crawl up toward the light which is admitted only through the glass bottle. When the bottle becomes at all crowded, it is replaced by an empty one. The vegetable debris which remains in the box is removed frequently, before it becomes so tightly packed that the creatures have difficulty in squeezing through it. Separators are not sold by the scientific supply houses, and if you want one you will have to make it yourself. Remembering the principle by which it works, you can use whatever materials are most con- venient to you. The separator shown in fig. 6 is made of a large metal cracker box, such as some grocers use. The glass bottle is a pint canning jar, the kind with a flat glass lid held down by a threaded metal rim. This rim is soldered to the box, and surrounds an opening almost as large as the mouth of the jar, which can thus be screwed onto the box in a moment, and just as readily replaced by a similar jar. The receiving hole in the lid is equipped with a wide-mouthed