Insects 157 



large size. The very large ones, often nearly three inches long, 

 seen flying over ponds, belong to the genus Aeshna. The wings 

 are clear and transparent, but the body is prettily marked with 

 green or light blue, the colors unfortunately difficult to preserve 

 after death. Because of their powerful flight, some of the species 

 of Aeshna have become very wide spread; thus A. juncca of 

 Europe is also found in Colorado; A. palmata, originally described 

 from Kamchatka, has been collected at Twin Lakes. It used to 

 be supposed that we had little to learn about these common and 

 conspicuous dragon-flies, but this was due to taking things for 

 granted, without proper investigation. In the summer of 1906 

 Dr. E. M. Walker of Toronto was at Lake Simcoe, Ontario, and 

 seeing the species of Aeshna in unusual abundance, began to 

 interest himself in their structural characters. To his astonish- 

 ment and that of other entomologists, he discovered that there 

 were several kinds which had been overlooked and confused with 

 those previously described. The final result was the publication 

 by Dr. Walker (1912) of a Monograph of North American Aeshna, 

 one of the best studies ever made of a group of insects. Dru 

 Drury, goldsmith, of London, (1725-1804), was a pioneer among 

 amateur entomologists. For many years he did everything in 

 his power to secure specimens of all orders, from every accessible 

 part of the world. We find him writing to a correspondent in 

 Virginia (1770), "Insects are my darling pursuit, therefore any 

 that come under that denomination either large or small will 

 meet a hearty reception." In 1 767 he was writing to Mr. Thomas 

 James of New York, urging him to obtain dragon-flies, and telling 

 him how to rear them from the larvae. "Get a large Buckett, 

 pail or washing tub, and put in it some weeds that grow in ye 

 water, fill it three parts full with water, and in ye spring search ye 

 waters above mentioned for Insects and put in as many Libella 

 cats as you please. Be sure to put in a great many of ye small 

 sorts, because ye large sorts prey and feed on ye small ones as 

 you will have opportunities of observing. If you find the number 

 of small ones decrease very fast you must supply the tub with 

 fresh ones, and once in three weeks or a month change ye water. 

 You must make a contrivance of a frame covered with gauze to 

 go over ye Buckett or Tub so that when ye Libellas are bred 

 they cannot fly away." The result of all this effort was that 



