IOWA ACADEMY OF SCIENCES. 223 



Mr. Robertson has given quite a full list of the insects 

 found on Cniciis discolor, C. altissinins and C. laiireolatus, 

 at Carlinville, Illinois. According to this writer the fol- 

 lowing insects are found upon Cnicus lanceolatus: 



Hymenoptera-^4j9/^«?.- Bomhiis amerlcanorum F.; B. vir- 

 ginicus Oliv.; B. pennsi/lvaniciis DeG.; B. separatus Cr.; 

 Mellissodes desponsa; M. ohliqua Say; M. coloradensis ; M. 

 bimaciilata Lep.; M. dentiventris; M. aurkjenia Cr.; Mega- 

 chile lafimanus Say; M. sexdentato, Rob.; Epeolus remigatus 

 F.; Andrenidce: Halictus ligatus Say; H. ipilosiis Sm.; Aga- 

 postemon, viridula F.; A. radiatus Say. 



he^idopterai-Rhopalocera Danais archippas F.; Phyciodes 

 tharos Dru.; Pier is protodice B.-L.; Colias philodice Gdt.; 

 Papilio turnus L. and P. glaucus L.; P. aster ias F.; P. troilus 

 L.; Pamphila peckius Kby.; P. cernes B.-L.; Eudamus 

 hathifllHS S. and A.; Heterocera Scepsis fidvicollis Hbn. 



Dipfera-Bouibi/lidce: Exoprosopa fasciata Mcq.; Si/sfce- 

 chus vulgaris Lw.; Conopidw: Phi/socephala tibialis Say. 



On Cnicus altissiiifus he reports the following: 



Hymenoptera- Apidce : Bombus americanorum F.; B.penn- 

 sylvanicus DeG; Mellisodes desponsa. 



Lepidoptera-Rhopalocera: Argynnis cybele F.; Papilio 

 troilus. 



He observed the following visitors upon Cnicus discolor: 



Hjmenoptevai-Apidcp: Bombus separatus Cr.; B. scute- 

 laris Cr.; B. pennsylvanicus DeG.; B. americanorum F.; B. 

 virginicus Oliv.; Mellissodes desponsa Sm.; M. obliqua Say; 

 Megachile latimanus Say; Andrenidce: Colletes eulopki Rob. 



heyiidopter^i-NyinpJialidw: Argynnis idalia Dru. 



Dipteva-Bo)n byl idee Exoprosopja fasciata Mcq. 



Dissemination. — Not a few writers have discussed the 

 question of the dissemination of the thistles. Among the 

 writers discussing these I may mention Weed "Ten New 

 England Blossoms," Hamilton Gibson "Sharp Eyes," and 

 numerous works dealing with the weedy character of 

 these plants. The fruit of all species has essentially 

 the same structure. The smooth achenes bear at their 

 upper end the limb of the calyx called the pappus, which 

 consists of a large number of plumose bristles. However, 



