12 THE YOUNG NATURALIST. 



they deposit over three times the number of eggs of most other Geometers. 

 I have seen large beech trees almost leafless from their destructive power. 

 All things are created for a purpose, all things work together for good ; there- 

 fore it is a blessing they are " helpless females " as Mr. Pierce terms them, 

 and, I believe, they enjoy life as well as if they had ample wings. 



I may say I have had some experience of antiqua } another of the species 

 with minature winged females. One afternoon, on a sweeping ramble for 

 larvse, I went to a fine patch of heather three or four acres in extent. I com- 

 menced operations by two or three sweeps with my net, and looked at the 

 contents. The result was I saw more antiqua larvse in my net at one time 

 than I should have considered a good afternoon's sweeping of mixed species. 

 However, I emptied my net as I did not require them, nor did I know any 

 one that did. I resumed operations again with the same result. In fact it 

 was antiqua ! antiqua ! antiqua ! and nothing else. The heath was alive 

 with them, and I just ask you to imagine such a plague as this if the female 

 could fly where it would. 



The subject is the origin of apterous females. Take a crippled female of 

 any other moth, the eggs do not produce cripples, far from it, the progeny 

 always have fully developed wings. But if it be the case that those " helpless 

 females " ever had fully developed wings, it would be reasonable to expect at 

 least one of the brood to have imperfect wings. We have no record of such 

 an occurrence, nor are we likely to hear of one. 



Mr. Pierce says it is a knotty subject to solve — he has made little progress 

 yet. 



Glasgow, Nov., 1886. 



EXCHANGE. 



I do not think that "Omega" apprehends the real use of exchange ; although 

 some of the cases he cites are peculiar, they do not touch the point. Suppose 

 a gentleman living in a city, closely engaged in business, with the exception of 

 a short summer holiday, captures a quantity of a common species, or rears 

 them, and that another collector similarly situated has caught a lot of another 

 species equally common, obviously it is a mutual advantage to effect an ex- 

 change, neither being able to get the insect which the other possesses in plenty. 

 Again, most entomologists only collect one particular branch, as Lepidoptera, 

 and another Coleoptera. Why should not common butterflies and moths be ex- 

 changed for equally common beetles ? It may be answered, get them for 

 yourself. In the first place, that is out of the question, as either bi anch is 



