210 



its natur;il food plants. The in nor side and angle of the antenna! tubercle 

 is stron,<;ly |)r<)niinent, rounded, ;iiid finely serrate, and the first anteiuial 

 joint is siniiliirly modified hut in a less degree (Fig. 219). There is ;. 



large dark patch on the disk 

 of the abdomen. 



Rhopai.osiphum dl\nthi 

 Schrank. 



This species has l)(>en 

 observed by Williams in a 

 greenhouse in Nebraska on 

 a number of different plants, 

 including corn. It is else- 

 where i-eported from a few 

 greenhouse and garden 



Fio. 219. Alyzus achyrantes, liead and aiitciiiia. < , _ 



Greatly enlarged. plants. 



The Yellow Sorghum Plant-louse. 

 Chaitophorus flavus Forbes. 



This lemon-yellow, short, bristly plant-louse (Fig. 220, 221), some- 

 times abundant and destructive on sorghum and broom-corn, has been 

 found by us in small mnnlxM-s breeding on leaves 

 of corn also, in late June and early July. In 

 September it occurred in all stages on corn leaves 

 in an experimental breeding-cage. It rarely infests 

 corn, however, even in the near vicinity of seri- 

 ously infested sorghum fields. 



Cornicles are j)resent but (]uite short, not 

 longer than broad. The species resembles the 

 box-elder plant-louse, Chaitophorus ncgmidiriis, but 

 that has six distinct antennal joints, not count- 

 ing the terminal spur, while fJavus has only five 

 joints, or often but four in wingless females. It 

 was found by me in June on young sorghum plants 



1,1 ,. • 1 ' 1 • 1 1 • 1. Ein. 220. The Yellow 



only three or four niches high, and in each sorKiium Pinnt - 1 <> » s e. 



of the following months up to late September, [ess'fem'ale.' Greatly'en- 



l)ut in October none were to be seen. The whiter "'*^^* ' 



history remains unknown. It also occurred on foxtail- and panic-grass 



(Setaria and ranicum) in the vicinity of infested sorghum plants, and 



has been taken by us breeding on grass in May, and on wheat in Sep- 



teml)er. 



Although most plant-lice prefer the growing tops of their host plants, 



