250 APPENDIX. [No. XV.B. 



THE POTATO DISEASE EXTENSIVE DISAPPEARANCE OP APHIDES. 

 From the ' Illustrated London News.' 



At various times I have had occasion to call the attention of the 

 public to facts connected with this destructive tribe of insects, and, in the 

 present instance, have to relate other circumstances connected with their 

 natural history which cannot fail to gratify the people. The importance 

 of bringing every fact before the agriculturist as it occurs must be appa- 

 rent to all ; for it is upon a correct knowledge of the habits of these 

 creatures that the farmer must estimate the probable damage when his 

 crops are unfortunately attacked. 



During this year the bean aphis has committed most serious damage. 

 It has killed plants in some places to such an extent that not one pod is 

 left; and even over large fields the crop will not nearly yield the seed 

 sown. The insects continued to increase up to a certain point, and then, 

 without reference to the destruction of the plants on which they were 

 located, took wing, and formed an army formidable from, their numerical 

 strength, which appeared completely to fill the atmosphere. The entire 

 number assumed the winged state within a few days, and left nothing 

 behind but their cast skins. The winged insects settled upon any palatable 

 food. They fled by thousands upon the beet-root, on which I have observed 

 them feed in a former year. When they alighted, they sucked the juices 

 of the plant in the ordinary manner, and sometimes killed the leaf of the 

 plant, which exhibited dark, black blotches. They, however, were not 

 doomed to remain long in this situation ; they speedily died, and have not, 

 in many cases, left a solitary individual to continue the brood. Those 

 which alighted upon the outdoor cucumbers were singularly destructive. 

 They settled upon the under-surface of the leaves in great swarms, and 

 fed upon the plant. Some of the attacked plants died from the injury 

 they sustained ; in others the leaf alone was damaged. I have been much 

 interested in watching the destruction of the cucumber : for I have heard 

 that during the last two or three years this plant has gone off in some 

 mysterious manner for which the farmer could not account. In the 

 instances which have come within my observation, every insect has 

 perished, and but a few of the whole plants were destroyed, on account of 

 the short duration of the attack. 



The bean aphis also alighted upon scarlet runners, French beans, 

 parsnips, onions, and various other plants and weeds. Groups of large 

 masses of dead winged insects may still be observed, although scarce one 

 live insect exists. 



The Aphis vastator has also, in those districts which I have examined, 

 become scarce. I do not know what has become of them all, but many 

 have been devoured by ladybirds, some have been killed by ichneumons, 

 others became unhealthy and perished. In proportion as the potato plant 

 is strong and healthy, so does it resist the attack of this parasite. The 

 puncture of the aphis hence is in some instances merely followed by a 

 little black spot ; in others by a large black botch ; and again, it may be 

 followed by a more or less complete destruction of the entire plant. In every 

 instance where aphides have been feeding, although they have now dis- 

 appeared, it will be found that the leaves are apt to perish, and the dying 



