372 



witbout. I have fully verified Trelease's statements by dissectiou and 

 study of the msects seeking this scant nectar, and indorse his conclu- 

 sion that while the observations serve to disprove any positive value of 

 their nectar in the pollination of Yucca flowers, they add to the impor- 

 tance of Pronuba by showing that the acts of collecting the pollen and 

 transferring it to the stigma are performed voluntarily and without food 

 compensation as I was at first inclined to believe 



I have lately had the pleasure of studying Yucca whipplei in Cali- 

 fornia and the remarkable Tree-yucca ( Y. brevifolia) in the Mojave desert. 

 The former is pollinized by Pronuba maculata Riley, and the latter by 

 a most remarkably modified and adapted species which I expect to de- 

 scribe as Pronuba jiaradoxa. 



Tlius everywhere in the United States where Yucca nominally fruits 

 we find it associated with its Pronuba, 



I await with interest and curiosity any new discoveries in tliis con- 

 nection, but, so far as present knowledge justifies anticipation, I should 

 expect, where neither Pronuba nor Pronuba-like insect exists, to find 

 the plant modified to more readily permit self-fertilization sooner than 

 to find Apis melUfica the pollinizing agent, the opinion of Mr. E. L. 

 Layard, of New Caledonia (who first expressed it in 1880 — Nature^ Vol. 

 XXII, p. COG), and of Mr. Hulst, to the contrary notwithstanding. 

 ] Reprinted from Proceedings Entomological Society of Washington. Vol. 

 /, No. 3,2>P' 150-154, read June 5, 1888.] 



NOTES OX SOME SPECIES OF INSECTS WHICH AFFECT THE UP- 

 PER PORTION OF THE STEMS OF SOME GRASSES. 



By F. M. Webster. 



There are several species among our common grasses which are more 

 or less subject to injury at or near the upper joint, whereby that portion 

 of the culm above is so injured that it will suddenly wither, turn yellow, 

 an<l die, leaving the portion below this upper joint green and vigorous. 

 Of the grasses thus atfected that have come under my own observation, 

 those most commonly injured are Blue-grass {Poa pratensis), Timothy 

 {Phleum pratense), Bottle Grass {Setaria glatica), and Panic Grass {Pan- 

 icuni crus-galli). 



The extent to which Blue-grass is subject to this attack in the United 

 States, east of the Mississiiiiii and north of the Ohio Elvers, has at- 

 tracted considerable attention, as it has also in Canada. 



In his Third report as State Entomologist of New York, page 96, Pro- 

 fessor Lintner calls attention to the fact that similar injury to this grass 

 was observed long ago and recorded in the Quarterly Journal of Agri- 

 culture and Science, 1, 1845, page 203. Professor Lintner in this notice 



