29 



"base of the front wing, and as that enlarged the wing expanded, very slowly at first, hut 

 more rapidly as it increased in size, the green colouring matter flowing along between 

 the upper and lower membrane of the wing, becoming more delicate in its shade as it 

 spread first along the front of the wing, and had reached the apex before it extended 

 through the inner half ; but by the time it had touched the extremity of the whole outer 

 angle the size, form and colour of the wing were complete. 



In the meantime the hind wing had not yet doubled its original size, with the part 

 from which the tail was to come showing as a slight break on an otherwise even edge ; 

 the same routine was followed in the development of the hind wing as that of the front, 

 and by the time the broad part of the wing 

 had attained its full size, the tail was a little 

 more than half an inch long and very much 

 crumpled. This was the last part to expand, 

 but as the fluid passed into it, it also took 

 size and form. The whole time occupied in 

 the operation, from first seeing it until it was 

 completed, was about an hour and three- 

 quarters. 



For the benefit of those of our readers 

 who may not be familar with this insect in its 

 earlier stages a larva nearly full grown is 

 shown in figure 15. It is a very handsome 

 caterpillar of a bluish-green colour with a pale 

 yellow stripe along each side of its body, the 

 spaces between the segments traversed by 

 lines of the same colour and each ring adorned 

 with small pearly warts from every one of 

 which arises a small cluster of short hairs. 



Experiments with Yeast in Destroying Insects. 



By Dr. H. A. Hagen, Cambridge, Mass. 



We are indebted to Dr. H. A. Hagen, of Cambridge, for the following letter and the 

 subsequent remarks on this interesting subject : 



Kingsnorth, Ashford, Kent, Dec. 27, 1881. 



Dear Sir, — I beg to thank you very much for your letter, dated Nov., 1880, respect- 

 ing the application of yeast for destroying insect pests. During the past season I have 

 endeavoured to follow the instructions contained therein, and as you express a wish to 

 hear of my success or failure, I will attempt to describe my experiments as clearly as 

 possible. As soon as Aphides became noticeable, I procured some German compressed 

 yeast, dissolved an ounce in a little warm water, added a little coarse sugar, and set it to 

 ferment. In about twenty-four hours I added sufficient water to make up a gallon, and 

 with this syringed a cherry tree attacked by black Aphides. This was on the 16th of 

 June. Four days later I found the tree almost clear of living Aphides, though their 

 dead bodies, or cast skins (I could not ascertain which, although I asked the assistance 

 of an entomological friend) smothered many of the leaves. One remarkable point in 

 this experiment was that a small branch of the tree, loaded with Aphides, hung over a 

 window, and, at the request of my wife, I abstained from syringing it. Here the insects 

 remained perfectly healthy, and after a few days were seen to work down the tree and 

 attack the young shoots that had been washed clean. On June 29th I again dressed the 

 tree, and this time destroyed or drove away every Aphide. I may add that the larvae of 

 several Aphidivorous insects were present on the tree, and did not appear greatly 

 affected by the application. Encouraged by the apparent success attending the applica- 

 tion, I commenced operations, June 20, on a second cherry tree. This, however, was 

 heavily leafed, and I could not make so much impression, but they evidently did not like 



