286 THE SCHOOL OF R:fiAUMUIl 



his chief thoughts to philosophy, and wrote much that 

 was once highly esteemed, though it has failed to endure. 

 Bonnet and his wife (a daughter of the celebrated De la 

 Eive family), being childless and wealthy, adopted a 

 nephew of Madame Bonnet, who made for himself a 

 great name as a botanist, a geologist and an explorer of 

 Mont Blanc. This was Horace Benedict de Saussure 

 (1740-1799). 



Experiments on Aphids 



To the Traite d' Insectologie is prefixed a short intro- 

 duction, for which Reaumur's Histoire des Insectes 

 furnishes all the facts, and all the figures of insects. 

 Bonnet then proceeds to explain the experiment pro- 

 posed to him by Reaumur, and the measures taken to 

 carry it out. He filled a flower-pot with earth, and 

 plunged into it a phial of water, intended to supply 

 the food-plant. A new-born aphis, whose birth had 

 been observed, was placed on the plant, and all was 

 covered up by a bell-jar, which was pressed into 

 the earth, so as to exclude other insects. An aphis 

 found upon the spindle-tree was selected for the first 

 trial, which began on May 20, 1740. Bonnet kept 

 an exact diary of his observations, which were made 

 hourly or oftener during the day ; a good lens was 

 continually employed. The aphis changed its skin 

 four times, and came to maturity on June 1, when the 

 first young one was born. By June 21 the unfertilised 

 female had produced 95 aphids, all born alive. She 

 was then accidentally lost, having by this time assumed 

 a peculiar shape (flattish, narrowed in front and rounded 

 behind), which GeofFroy had mistaken for the male 

 aphis, but which E^aumur had shown to indicate an 

 exhausted female. Next year the experiment was re- 



