18 BRITISH APHIDES. 



and covered the walls of the houses so as partially to 

 conceal them. 



I have no doubt that the Aphis figured by Mr. Smee 

 in his work on the potatoe plant, under the name of 

 Ajiliis vastator is Aphis dianthi of Schrank and other 

 authors. Amongst the numerous food-plants he men- 

 tions, we find the poisonous Atropci belladonna, Sola- 

 num didcamara, vindi Eufliorhia pephis. 



That there is any necessary connection between the 

 potatoe disease and the attacks of this Aphis on the 

 haulm it is believed no one now can reasonably 

 sustain ; yet it is undoubtedly true that a sickly and 

 diseased condition is induced on many plants through 

 exhaustion caused by the crowding and swarming of 

 Aphides. It is not improbable that Aphides, like 

 many of the Cimicidas, throw highly irritant juices, 

 elaborated by their salivary organs, into the wounds 

 made by the piercing set^e of their rostra. These 

 juices may assist in the preparation of the sap for 

 assimilation by the insect. 



Mr. Berkeley has urged that the commencement 

 and root of the potatoe disease is to be traced to the 

 ramifications of the mycelial threads of the fungus, 

 Pero7iospora infestans, which burrows throughout the 

 substance of the potatoe tuber, stem, and leaf. 



Mr. W. G. Smith has recently made the very 

 remarkable observation, that the penetration of the 

 above mycelium is not confined to vegetable tissues 

 alone for its propagation. An examination of nume- 

 rous specimens mounted in balsam for the micro- 

 scope has led him to believe that these fungoid 

 spawn-threads grow both outside and inside the 

 bodies of Aphides. " Sometimes the oogonia, which 

 eventually become resting-spores, are deeply buried 

 in the body of the Aphis, whilst the whole insect 

 is traversed by mycelial threads ; many of the oogonia 

 are inside the legs, sometimes inside the feelers." 

 " These oogonia and antheridia are presumedly the 

 same with those found in diseased potatoes. The 



