116 PROTKCriON OK PLANTS. I<M6-17 



year I have been able to draw a new conclusion from personal observation, 

 namely, that the Colorado beetle is fond of ornamental tobacco (Nicotiana 

 affinis). In a garden when some fifty plants of this variety had been set, 

 this insect devoured them as greedily as potato plants, attacking both 

 leaves and flowers. The idea then occurred to me that the potato bug 

 might become the bug of all the Solaneoe and this I tried to ascertain. 1 

 had at my disposal tomato plants, petunias and ordinary tobacco. A good 

 many persons had assured me that the potato bug does not eat tomatoes. 

 I resolved notwithstanding to extend my experiment to these also. The 

 lirst tests consisted in transferring eggs, larvae and perfect insects to some 

 petunias, tomato and tobacco plants. The failure was complete, neither 

 larvae nor insects wishing to eat. They tasted the leaf, then departed ; the 

 insect undertaking a long journey, the larva generally burying itself in 

 the ground after having explored the neighbourhood. I had taken my 

 subjects now from the potato, now from the ornamental tobacco. I was 

 especially surprised to see that the larvae from the ornamental tobacco 

 absolutely refused the ordinary tobacco; a few of these larvae transferred 

 from the potato to the ornamental tobacco had not seemed to notice any 

 difference, but transferred from the latter to the ordinary tobacco they left 

 immediately. After many trials I concluded that neither the larvae nor the 

 perfect insects attack the petunia, tobacco or the tomato if they are free. 

 The insects coming from eggs hatched on the leaves of these same plants 

 show the same state of mind: they die on the spot if their strength does not 

 permit them to migrate. 



I was pleased to see the tomato and tobacco spared. However an 

 important question remained: in case of famine, isolated in a field where 

 they would find no other food would the larvae and the insects die of starva- 

 tion rather than eat a food belonging to the same family as their favorite 

 food? In the above mentioned experiments where the subjects were given 

 entire freedom, it was impossible to see how hunger would make them act, 

 sinceall left and soon disappeared. I thcnmade prisons out of boxesand shut 

 up the larvae and perfect insects taken from ornamental tobacco and potato 

 plants. In a few of the boxes I placed petunia leaves, in others tobacco and 

 in the remaining ones tomato leaves. Here is what I observed: The per- 

 fect insects, far less greedy, held out very long, walking all over the leaves 

 and examining them minutely. The relatively insignificant quantity which 

 tliey eat renders the observations extremely difficult. At times they stop 

 and seem to press their mouths upon the leaf but after they leave, no change 

 can be noticed. Have they really eaten? Impossible to decide. I kept 

 a few for three weeks in empty boxes; and they survived. What had they 

 eaten? The boxes seemed intact. The observations were so difficult that 



