408 NOTES AND MEMOKANDA. 



which constitutes the first generation in a very remarkable series, 

 settling upon the tender opening loaves. This " stem-mother " begins 

 to feed, causing the leaf to swell up and pucker until it at last curls 

 over the tiny form. After three moults, and the temperature being 

 warm, it commences to people the leaf with young at the rate of 

 about one every six or seven hours. The second generation, though 

 they never grow to be at all as large as the stem-mother, are like her 

 in many respects. They accumulate in vast numbers, some of which, 

 scattering, form new colonies. Their issue forms the third generation 

 which are destined to become winged. These winged forms are short- 

 lived, but they lay twelve or more j)seudova at average intervals of 

 about half an hour. The young plant-lice from these form the fourth 

 generation, the members of which are very active, running swiftly. 

 They are of a brown colour, and are somewhat like in general appearance 

 to those of the second generation. In this stage they swarm over 

 every portion of the tree, and their necessities cause them to migrate, 

 in which effort masses of them get destroyed. The fifth generation is 

 very similar to the fourth. It gives rise to forms like the fourth, but 

 without wings. These give origin to the sixth generation. All of 

 these acquire wings. These abound in the latter end of June and 

 early part of July. They congregate on the bark, seeking out sheltered 

 cracks or crevices, in which they deposit their young. These form 

 the seventh generation, and are sluggish, of the colour of the bark, 

 the females a little larger than the males. They have no mouth. 

 They live for several days without motion. The female seems to 

 increase in size by the enlargement of her one single egg. Both sexes 

 soon perish, leaving among their shrivelled bodies the shining, brown- 

 ish, winter egg with which we started ; so, after a long series of vege- 

 tative reproductions, at last the time comes f(jr the renewing of the 

 race by this zygospore-like body. Sm-ely in this lies a hint to our 

 plant-growers. It would be easier to destroy a single egg than stop 

 a stream of agamic-produced forms extending to six generations.* 



Buzzing of Insects. — In a supplementary communication on this 

 subject (see vol. i. pp. 276 and 373), M. Perez says that he does not 

 agree with M. de Bellesme in thinking that a conical movement 

 (mouvement conique) of the thorax can produce a sound, because, on 

 fixing the animal with a pin, the movements are very attenuated, with- 

 out the movements of the wings and the buzzing being destroyed or 

 even weakened. These movements cannot therefore explain the 

 buzzing, f 



Larval Cases of Phryganeidse.— Several new forms of Phryganeidce, 

 exhibiting interesting modifications of the larval cases, have been dis- 

 covered in Brazil by Fritz Mixller, who describes them in a letter to 

 his brother Hermann Miiller. J He says, " I have lately found several 

 new larvfe of Phryganeidce. The group of Hi/droptilidiB seem parti- 

 cularly rich in this place in peculiarly shaped larva-cases. Hagen 



* 'Times,' 12tli March, 1879. 



t 'Rev. Iiiternat. Sci.,' iii. (1879) 281. 



X ' Zool. Auzeiger,' ii. (1879) 38. 



