NOTES ON COLLECTING, ETC. 81 



being set, and ammonia leaves them very flaccid after death. The spe- 

 cimens are apt to verdigris, and so black pins should always be used." 

 Now, I never kill with ammonia myself, simply because I have a 

 theory that all specimens strongly impregnated with it are apt to 

 corrode the pins, whatever kind are used. Those who are in the habit 

 of using ammonia will probably say I am under a misapprehension, 

 but I have found that certain species which never corrode my pins do 

 corrode the pins of some of my correspondents, and I should much 

 like to have the opinion of a practical chemist on the subject. As to 

 black pins, after long experience I have come to the conclusion that 

 for the purpose of preventing verdigris, they are perfectly useless. I 

 regarded them as a delusion and a snare when they were first intro- 

 duced, because it seemed to me that japan varnish would certainly be 

 soluble in the acrid fatty matter which some species unfortunately 

 contain, and on writing to a pin manufacturer whom I know, I found 

 he was quite of my opinion ; moreover, he said that in order to get 

 the varnish on, it would be necessary to subject the metal to so much 

 heat that all the " temper would be taken out of it, which would cause 

 the pins to bend easily and to turn up at the points. The only way I 

 know to prevent verdigris, is to extract the fatty matter — by immer- 

 sion in benzoline or otherwise — before the pins have become green. I 

 operate on large numbers of specimens every winter, and thus save 

 many that would otherwise be utterly spoiled. Very likely the varnish 

 may protect the metal to a certain extent for a limited time, just as 

 gilding does, but it is a mere question of time. I use black pins 

 myself, simply because I cannot atford to be wiser than the majority of 

 other people — for some collectors still say, " Do not send me any 

 black pinned specimens " — but when I remember how much more easy 

 and pleasant it was to pin some insects — the smaller Hymenoptera for 

 instance — with pins that had points, I cannot help grieving over the 

 success of mis-directed cnteri:)rise. — ^V. H. Harwood, 2, Brooklyn 

 Villas, Colchester. February 22}id, 1S92. 



The experience of Mr. Harwood is, I admit, probably far beyond mine, 

 on this important subject; but still, I have set so many specimens during 

 the last twenty years, »:hat I cannot get away from actual facts. First, 

 with regard to the action of ammonia on pins. It is, I suppose well- 

 known, that ammonia readily affects the metal and forms chemical com- 

 pounds with it. Place a few white pins and a few black ones in a box, 

 and then pour a drop of liquid ammonia into it. A few minutes, and 

 the white pins are quite green, and shortly after the black pins also, 

 especially if badly japanned. But, do insects absorb sufficient ammonia 

 to affect the metal, and secondly, if so, do they not part with the 

 absorbed ammonia, on exposure, too rapidly to affect the pin ? I 

 have some t,ooo specimens of Pterophori in my collection, and scarcely 

 a single black pin has corroded, and all my specimens have been 

 killed with ammonia. Those that have come from correspondents on 

 white pins are very different, and are gradually getting thickly coated 

 with verdigris, and the insects are posturing at all angles. My Tineina 

 are, generally, as free from verdigris, and so, comparatively, are my Tor- 

 trices. Of course, insects on some black pins do verdigris. Tayler's 

 pins have such large heads, but compared with Kirby, Beard and 

 Co.'s pins, the bad pins are probablv less than 1:20. In fact, 25-50 



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