294 



THE AMERICAN 



HOW TO COLLECT AND STUDY IISECTS-No. 5. 



BY F. G. SABBOKN, BOSTON, MASS. 



"While speaking of tlie microscope and its iisos 

 in studying living insects, I should mention a 

 method of preparing specimens and fragments 

 illustrating the structure or anatomy of these 

 minute beings, so that they may be preserved 

 indefinitely for future use. The ordinary size 

 of a " slide " for the microscope is, as I previ- 

 ously said, three inches in length by one in 

 breadth. The slide should be cut from clear and 

 rather thin glass, free from, flaws and air-bubbles, 

 and a few dozen should be kept constantly on 

 hand ; they can be easily and cheaply got out by 

 any glazier from his waste slips. If the student 

 wishes to have them finely finished, he can grind 

 the edges smooth upon an emery wheel, a com- 

 mon grindstone, or even upon a flat surface with 

 emery powder and water, at the expense of a 

 little more time and labor. The " covers " will 

 cost lum rather more care, as the exceedingly 

 thin glass which is prepared for thiS purpose is 

 not to be prociu-ed except in large cities, where 

 an ounce of circular covers of various sizes gen- 

 erally costs about three dollars. The thinnest 

 glass he can procure will answer for many ob- 

 jects if clear; and even mica, which separates 

 readily into thin plates, and can be readily cut 

 with scissors, serves a very useful purpose, al- 

 though liable to injury from scratches. The 

 covers need not be round ; square or oblong ones 

 are just as good. Cut on an average one-half 

 inch square ; few will be required larger, and the 

 majority of specimens will be covered by a one- 

 quarter inch cover. Having a supply of these 

 ready for use, obtain a vial of fir or "Canada" 

 balsam, thin it with chloroform aud keep tightly 

 corked. "Whenever a small insect, a mite, a 

 gnat, or a young larva, just from the egg, is to 

 be preserved, place it upon the centre of a clean 

 glass slide, let a drop of the balsam fall upon it, 

 and apply the cover. A little experience will 

 enable one to avoid " air-bubbles " and such 

 inconveniences, and show how long the prepar- 

 ation requires to dry and harden, as well as what 

 weight to apply to the cover. English opera- 

 tors use a very efl'ective and simple contrivance 



[Fig. 1S3.] 



of wire as in Figure 183, and easily made of 

 difierent powers of compression suitable to the 



object. The specimens thus prepared should 



be kept in boxes lined with grooved slips of 



wood as in Figure 184, having the grooves op- 



[Fig. :s4j 



posite, ajid of such depth and distance apart 

 as to keep the slides separate and safe from 

 breakage. The slides may be numbered or la- 

 belled oil the glass with a diamond, or bit of 

 hard stone, such as a quartz crystal; or have 

 paper " adhesive tags " pasted on one end, as in 

 our sketch, according to the taste and skill 

 of the student. To return to our collecting. 

 Let us follow the course of this old stone wall, 

 from whicli have fallen at various times numbers 

 of loose rocks; under many of these will be 

 found forms of life to repay a careful search. 

 But here on the very top of the wall is a crawl- 

 ing thing which we drop into our vial of alcohol 

 with some little repugnance at tlie touch. "An 

 Earwig?" Not precisely, but sometimes impro- 

 perly so called. It is not even a true insect, but 

 belongs to the Centipede family of articulated 

 or jointed animals. As you will see, it has too 

 many feet for an insect, or even the larva of an 

 insect. Some naturalists would by a careless 

 use of terms consider it an insect, but we prefer, 

 in accordance with the laws of priority, to con- 

 fine that title to tlie true three-jointed articulates 

 wluch have in the adult condition six legs only. 

 This, as you see, has many joints or segments, 

 and numerous feet, although full grown. The 

 Class to which it pertains is called Myriapoda, 

 or many-footed animals, from this feat-vxa 

 (no pun intended) of its structure; and this 

 species, Lithobius americanus, or the American 

 dweller under stones, is very much unlike the 

 true Earwig, Forficula, in everything but color, 

 and is very abundant throughout the United 

 States in damp localities beneath stones and logs. 

 In fact, we should not have seen this specimen 

 so liigh above the groxmd were it not for the 

 moist condition of the lichen-covered wall after 

 the recent shower. Here are others of the same 

 kind beneath this stone, aud a coiled Myriapoda 

 looking like a small shell, closely related to the 

 preceding, but very cylindrical and with a much 

 harder covering; as we disturb it, and it en- 

 deavors to make its escape, you perceive that its 

 feet are still more numerous than those of Litlio- 

 lius, aud move with a very beautiful continuous 

 undulating motion along the sides, reminding 

 one of ripples passing along the sides of a boat. 



