62 MAINE AGRICULTURAL EXPERIMENT STATION. ICjIO. 



The appearance of the infested oat plants is fairly character- 

 istic though as suggested above may resemble attacks of thrips 

 or plantlice. 



The most evident effect is the production of numerous spots 

 on the leaves these spots being at first whitish then turning to 

 yellow then to brown and later to black often a black or brown 

 center being surrounded by a reddish or yellow border and very 

 much resembling a fungus affected spot. This resemblance is so 

 great that the presence of fungi has often been suspected and 

 efforts made to determine it. In fact I have often been in 

 doubt whether certain spots could be charged to insect attack 

 or fungus and have hesitated to assign the injury to the insect. 

 The presence of eggs in the infested leaves or the demonstra- 

 tion of punctures where the hoppers have been sucking the 

 plant cells however will leave no question as to the cause. Prof. 

 Morse of this station who has made careful studies of these 

 injuries states that he has been unable to find fungi present i 1 

 connection with the spots except late in the season and when 

 they may very probably have followed as a sequence of the 

 hopper punctures. 



The egg punctures and the feeding punctures are different 

 enough so that they usually may be distinguished with the aid 

 of a lens and the egg punctures do not as a rule show the color- 

 ing which follows the punctures and sucking of sap where the 

 insects feed. The eggs are deposited mainly in the. upper pa ; *r 

 of the leaf sheath or close to the stem- on the basal part of the 

 leaf blade. They are forced in beneath the epidermis usually 

 close to the under epidermis but not through it and thus lie in 

 the layer of cells between the two epidermal surfaces of the 

 leaf. The result is a transparent spot that is usually quite 

 apparent especially if the leaf is held up to the light. 



The feeding puncture is by itself a very minute affair scarcely 

 to be detected except by magnification but the sucking of the 

 cell contents produces a deadened spot which as already de- 

 scribed changes color with time until it becomes brown or 

 black. The change in color may be assisted by the injection of 

 some secretion in the process of feeding which has a poisonous 

 effect on the plant tissues as is the case in some of the othc 1 ' 

 species of leafhoppers notably the species producing curlv leaf 



