Through a Microscope Part 6

Take for example the antennae. In the gra.s.shopper it is long and threadlike; in the b.u.t.terflies always ending in a k.n.o.b; in moths always tapering to a point, although sometimes threadlike and sometimes much branched, forming a beautiful plume; in the beetles, sometimes fan-like, sometimes like a comb; and in other insects a.s.suming still other forms.

Insects' eyes are often colored beautifully. A horse-fly's eyes are striped. b.u.t.terflies' eyes have usually a soft liquid coloring, and moths' eyes in the dark shine like little fiery beads.

The mouths of insects, such as beetles, gra.s.shoppers and dragon flies, have strong jaws for biting; flies, bugs, moths and b.u.t.terflies, have the mouth-parts transformed into sucking organs, while bees, wasps and the like have both sucking organs for honey, and biting organs for leaf-cutting, wood-tearing etc. as we saw was the case in the b.u.mble Bee.

b.u.t.terflies' wings and moths' wings are covered with little scales of a variety of shapes. These should be examined attached to the wing to show their arrangement which is like that of shingles on a roof; but to show their form they should be looked at when brushed from the wing onto a piece of gla.s.s. Many other peculiarities may be noticed in the wings of other kinds of insects.

Legs, the same as the other organs, have various forms, markings and appendages, and so it is with the abdomen and its stings or its egg-laying apparatus.

The hairs of "Wooly Bears" and caterpillars of that kind are peculiarly branched.

The four hind pairs of feet in caterpillars are armed each with a row of little hooks which are used in walking to get a firm hold. The larger caterpillars show the hooks best.

Sometimes you will find pretty insect eggs on the underside of leaves or on stems, and also little silken coc.o.o.ns in similar places. If you are near a pond-hole, or an old hogshead that collects rain water, you can find a good many little animals, some of them very frisky--young mosquitoes or "polywogs," water-fleas, cyclops, little worms, young dragon-flies and lots of others. When you go to collect them take a small wide-mouth bottle and, having found a place where there is what you want, lower your bottle, mouth down, in the midst of them and when it is well under water turn the mouth upwards. A good many of the animals will run in with the water. If the first time you do not get what you want, the second time you may. When you want to examine them at home you can fish them out with a gla.s.s tube and put them in a watch crystal or on the gla.s.s stage of the microscope. In using the tube take it between the thumb and middle and third fingers, and close the top with your first finger; then put the lower end of the tube in the water close to the thing you want to catch; now lift your first finger quickly and the water will run in the lower end of the tube carrying with it your little squirmer, unless he has been too quick for you. Close the top of your tube again and the water will not run out when you remove the tube, until you lift your finger. Sometimes it takes a good deal of patience and skill to catch the more agile of the little water animals.

Gla.s.s tubes are sold in drug stores for five or ten cents.

If you begin by examining the objects already spoken of, you will while looking for these be continually discovering for yourselves new objects possessing new beauties and will soon see that not half the interesting things you can find have been ever hinted at.

The way to find out about all these things is to go out into the fields and woods, and form the habit of observing closely what is around you.

Carry your magnifier along and look at this flower, that fern, this insect, that moss, with different powers of the magnifier; and when you come across any objects worthy of a more careful examination carry them home and examine them systematically with Simple microscope, needles, knife, and so forth. Insects may be kept well in alcohol until winter, and then careful studies may be made of them.

When using the magnifier in the field, hold it in such a way that the smallest lens will be nearest the object when the lenses are combined and be careful not to shade the object with the hand or the hat brim.

Just enough light should fall on the object to make its examination comfortable for the eyes. If you rest the hand holding the magnifier on the hand that holds the object, both lens and object can be held much steadier. When commencing to examine an object it is best to have the three lenses spread apart, for in this way you can use first the lowest power then those higher and finally, if you wish to, the three lenses combined. The dissecting forceps are very handy to have in the field, both for picking up anything too small for the fingers and for holding an object to be examined.

A collection of some of these little things preserved and ready for examination adds greatly to the pleasures of studying them. Of course all the different kinds of objects cannot be preserved so as to show their full beauty, but many can be and the following directions will tell how to make a very good collection:

Seeds, fern-fruit, insects and other opaque objects like these may be mounted on pasteboard slides. One of these slides consists simply of a stout piece of pasteboard, having a hole cut in the centre and a piece of thick paper or cardboard glued on the under side. The object is attached to the cardboard at the bottom of the hole.

It is best to make a number of these slides at a time. Having procured some quite thick pasteboard, from old paper boxes, rule lines on the surface dividing it up into s.p.a.ces three inches long by one inch wide.

In the centre of each s.p.a.ce cut out a hole about half an inch in diameter. A sharp knife will make a neat square hole or a good round one may be made with a gun-wad punch. This done, the s.p.a.ces may be cut apart with a sharp knife and ruler, along the lines already drawn. Pieces of cardboard for the backs should be cut a trifle larger than the pasteboard portion of the slide; after they are glued onto the latter they may be trimmed down neatly with a pair of scissors. Glue or mucilage containing glycerine (in the proportion of one or two teaspoonfuls to an ordinary bottle of mucilage) is the best thing to use for sticking on the backs. While the slides are drying they should be either under a weight or in a clamp screwed up tightly, so as to prevent their twisting out of shape. The mucilage may be prevented from being squeezed in round the edges of the hole, by taking care when putting it on not to have it come too near the hole. One or two coats of India Ink may be painted on the middle of some of the pieces of cardboard, either before or after they are put onto the slides; and thus a black background may be obtained for the lighter-colored opaque objects. Many of the objects will however show best on a white background.

When you have the slides all made, nothing more is needed to mount an object, than simply to attach it to the bottom of the hole with a little mucilage and glycerine, or something of that sort, and finally to write the name of the object on the front part of the slide, and on the back any desirable notes. A good way to mount such objects as fine seeds is to put them in the hole loosely and then cover them with a piece of mica such as will be spoken of presently.

Objects which are to be examined by the light shining through them, for example a bee's wing or a b.u.t.terfly's scales, must be mounted on gla.s.s slides.

A gla.s.s slide three inches by one is taken, on the centre is placed the object; over this is laid a thin piece of clear mica three fourths of an inch square, and this is attached to the gla.s.s by pasting narrow strips of tissue paper around the edges of the cover, partly on the cover and partly on the slide. Finally the slide is covered with some pretty colored paper and labeled.

Two pieces of paper are needed to cover each slide. One for the under part is cut about one and one half by three and one half inches, with a hole in the centre (round or square). This piece is first pasted on, the corners being cut and the edges brought over onto the front. The upper piece, which has a hole in the centre similar to that in the lower piece, and is cut a trifle larger than the three by one inch slide, is next pasted on so that the hole will correspond with the one below. The upper piece of paper is now trimmed down to the slide and the label attached. Window gla.s.s will answer for the slides and you can get any glazier to cut up a piece for you into the right-sized slips. Mica can be bought at a stove store, in sheets which may be cut up into three fourths of an inch squares with a pair of scissors. The mica should be as clear as you can get it. You will find it handy to have some tissue paper all mucilaged like postage stamps and cut up in strips the right size ready to use. The same may be said of the colored paper covers and the labels.

The dust may be excluded from the uncovered opaque objects by keeping the mounted slides in small groups, held together by elastic bands. This will also serve to cla.s.sify them so that all the insects will be together, all the seeds, and so on; and the transparent slides may also be treated in the same way. When an elastic band wears out, it is no great trouble to replace it.

In working with the Simple microscope there is a fine chance to display ingenuity, not only in making the instruments and mounting the objects but in discovering new things to look at and in seeing how much can be found out about those things which are the most common.

FOOTNOTES:

[A] In these directions "1-1/2 _in._ power" means a lens having a focus of 1-1/2 inches; "1/2 _in._ power" means a lens or combination of lenses having a focus of 1/2 inch; and so on. All the different powers mentioned in the directions may be obtained in the small-sized 3-lens, bellows form magnifier, either by using the lenses singly or combined in different ways. The magnifying power of any single lens or simple combination is easily found by dividing 10, by the focus in inches. Thus the magnifying power of a 1/2 _in._ lens is found in this way: 101/2 = 102/1 20. The lens magnifies therefore 20 diameters _i. e._ makes an object appear twenty times as long and twenty times as broad as it is.