1889.] NEW-YORK MICROSCOPICAL SOCIETY. 37 



Now it may strike us as curious that the last three segments of 

 the body of this larva should be provided with such an immense 

 number of "arrow-hairs," while each of the others carries only a 

 single row. The habit of the creature will, however, explain it. 

 When disturbed it generally rolls itself into a kind of ball, or 

 contracts its body in such a manner as to expose chiefly these 

 formidably armed abdominal segments. The "arrow-hairs" 

 then spread out in all directions, a bristling forest of bayonets, 

 in which a warm reception awaits the incautious intruder. 

 Insects, such as ants, etc., though protected by a hard, chitinous 

 envelope, have their vulnerable points. Their armor-plates are 

 generally joined by a membrane quite thin and soft and easily 

 pierced or irritated. 



I have gone to this length of description because I wished to 

 draw your attention to a remarkably beautiful object for the 

 microscope, which is easily obtained, though the preparation of 

 the slide is attended with some difficulties, owing to the ten- 

 dency of the hairs to become entangled when placed on the glass 

 slip. Attempts to separate them by means of fine needles are 

 mostly futile or result in a general demolishment. The easiest 

 way of preparing them is by securing the cast skins, which are 

 to be found in almost every insect collection. From these skins 

 the hairs can be easily detached and pieces of the skin can also 

 be mounted with the two kinds of hairs in. situ, or the entire 

 skin, after having been soaked awhile in turpentine, can be 

 spread out and mounted in Canada-balsam — a most beautiful 

 and interesting object. I have here, to-night, about a dozen of 

 these hair-slides, all prepared from cast skins, some showing only 

 the loose " arrow-hairs," others small pieces of the skin with 

 both kinds of hairs, and a few exhibiting the entire skin. 



You will find these larvae if you look for them, and if you 

 should not succeed, catch and kill half a dozen butterflies, put 

 them in a card-board box (in Spring or Summer, of course) and 

 I guarantee that in less than four weeks you will have as many 

 of the larvae, feeding on the bodies as you can manage to put 

 under cover-glasses. 



Of course I am not the original discoverer of these " arrow- 

 hairs." They were known, I dare say, long before my time, but 

 I have never seen a satisfactory description of them anywhere 

 and, considering their beauty and interest it is surprising to 



