IOWA ACADEMY OF SCIENCES. 
223 
Mr. Robertson has given quite a full list of the insects 
found on Cnicus discolor , C. altissimus and C. lanceolatus, 
at Carlinville, Illinois. According to this writer the fol- 
lowing insects are found upon Cnicus lanceolatus: 
Hymenoptera -Apidce: Bombus americanorum F.; B. vir- 
ginicus Oliv.; B. pennsylvanicus DeG.; B. separatus Cr.; 
Mellissodes desponsa; M. obliqua Say; M. color adensis ; M. 
bimaculata Lep.; M. dentiventris; M. aurigenia Cr.; Mega- 
chile latimanus Say; M. sexdentata Rob.; Epeolus remigatus 
F.; Andrenidce: Halictus ligatus Say; H. p ilosus Sm.; Aga- 
postemon, viridula F.; A. radiatus Say. 
Lepidoptera -Rhopalocera Danais archippus F.; Phyciodes 
tharos Dru.; Pieris protodice B.-L. ; Colias philodice Gdt.; 
Papilio turnus L. and P. glaucus L.; P. asterias F.; P. troilus 
L.; Pamphila peckius Kby.; P. cernes B.-L.; Eudamus 
batliyllus S. and A.; Heterocera Scepsis fulvicollis Hbn. 
Diptera-Bombylidce: Exoprosopa fasciata Mcq.; Systoe- 
chus vulgaris Lw.; Conopidce: Physocephala tibialis Say. 
On Cnicus altissimus 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: 
Hymenoptera -Apidce: Bombus separatus Cr.; B. scute- 
laris Cr.; B. penns ylvanicus DeG.; B. americanorum F.; B. 
virginicus Oliv.; Mellissodes desponsa Sm.; M. obliqua Say; 
Megachile latimanus Say; Andrenidce: Colletes eulophi Rob. 
Lepidoptera-A^/m^/m/i^: Argynnis idalia Dru. 
Y)i])ter&-Bombylidce Exoprosopa 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, 
