178 Trans. Acad. Sci. of St. Louis. 



cm., but the rays are inclined to droop. The discs soon be- 

 come elevated into a conical globular form. The ray florets 

 are neutral. Those of the disc are perfect, with erect lobes 

 and admitting an insect's proboscis to the extent of 3 ram. 

 The plant is common and blooms from July 17 to September 

 28. The following visitors were observed on August 13, 15, 

 17, 22, 26, 31, and September 10 and 12 :~ 



Hymenoptera — Apidae: (1) Apis melliflcaL. g , s. & c. p., ab.; (2) Bom- 

 bus separatus Cr. §, s. & c, p. ; (3) B. americanorum F. g , s.; (4) Melisso- 

 des obliqua Say 9> c. p. ; (.5) M. dentiveatris Sm. (^^, s. &c. p., freq. ; (G) 

 M. coloradensis Cr. J*, s. ; (7) M. autumnalis Rob. J^, s.; (8) M. confusa 

 Cr. (^, s.; (9) Calliopsis labrosus Rob. J*?, s. & c. p., freq.; (10) C. rud- 

 beckiae Rob. (^^, s. & c. p., freq.; Andrenidae: (11) Halictus llgatus Say $, 

 s. & c. p. ; (12) Andrena aliciae Rob. 9> s. & c. p., freq.; (13) Colletes com- 

 pacta Cr. (^^,8. &. c. p., freq.; Bembecidae: (14) Bembex fasciata F., s.; 

 Sphecidae: (15) Ammophila gracilis Lep., s., freq.; (16) A. iatercepta Lep., 

 8.; Scoliidae: (17) Scolia bicincta F., s. 



Diptera — Empidae: (18) Empis clausaiRob. (MS.), 8., freq.; Bomhylidae: 

 (19) Exoprosopa fasciata Mcq., s.; (20) Anthrax halcyon Say, s.; (21) A. 

 alternata Say, s.; (22) Systoechus vulgaris Lw., s., (23) Sparnopolius fulvus 

 Wd.jS.; Syrphidae: (24) Syrphus ribesii L., f. p.; (25) Eristalis transversus 

 Wd., s. ; (26) E. dimidiatus Wd., s. ; Tachinidae: (27) Jurinia smaragdina 

 Mcq., 8.; (28) Peleteria robusta "Wd., s., freq.; (29) Cyphocera fuesta V. d. 

 W., s.; (30) Acroglossa hesperidarum "Will., s. 



Lepldoptera — Bhopalocera : (31) Phyciodes nycteis Db.-Hew. ; (32) Lycae- 

 na pseudargiolus Bd.-Lec; (33) Pamphila cernes Bd.-Lec. ; Heterocera: 

 (34) Scepsis fulvicollis Hbn. — all s. 



Cacalia RENiFORMis Muhl. — The stems grow from 5 to 15 

 dm. high and are terminated by rather large flat-topped 

 corymbs of white heads. Each head contains five tubular 

 perfect florets. These open in succession, the ones in the 

 second stage being bent aside so that the stigma cannot 

 touch the anthers of the younger flowers. The tubes are 

 about 6 mm. long, very narrow below, but opening above 

 into a wider portion about 2 mm. long. Insects only insert 

 their proboscides into the wider part of the tube. The plant 

 blooms from June 25 to Aug. 1. The following insects were 

 taken on the flowers on June 25 and July 2, 8 and 16: — 



Hymenoptera — Apidae; (1) Apis melliflca L. g, s. ; (2) Melissodes 

 bimaculata Lep. $, s.; (3) Ceratina tejonensis Cr. (^, s.; (4) C. dupla Say 

 $, s.; (5) Heriades carinatum Cr. $, s. & c. p.; Andrenidae: (6) Halictus 

 foxii Rob. (^, 8.; (7) H.pectoralis Sm. J^9, s.; (8) H. cressonii Rob. (f^, s. ; 



