PART III. | THE MECHANISMS OF FLOWERS. 325 
the florets of the disk, possessing even the sweeping-hairs that are 
here useless from the absence of stamens. 
Visitors: A. Hymenoptera—Apide: (1) Heriades truncorum, L. ? ¢, 
_ very freq., s. and c.p.; (2) Halictus longulus, Sm. ¢; (8) H. maculatus, Sm. 
6; (4) H.albipes, F. ¢; (5) H. cylindricus, F. ¢; (6) H. nitidus, Schenck, ¢, 
alls. B. Diptera—Syrphide : (7) Eristalis arbustorum, L. ; (8) E. sepulcralis 
L., both species, fp., very ab.; (9) Melithreptus scriptus, L., fp. C. Lepid- 
optera—(10) Polyommatus dorilis, Hfn.; (11) Lycana sp. ; (12) Hesperia 
thaumas, Hfn., s. D. Coleoptera—Chrysomelide : (13) Cassida murrea, L., 
whose larva feeds on the leaves of this plant, often creeps about the flowers and 
effects cross-fertilisation. 
Tribe Helianthoidee. 
Zinnia, my brother Fritz Miiller tells me, is visited almost 
exclusively by Lepidoptera, especially Hesperidz, at Itajahy. In 
North America it is visited by ruby-throated humming-birds also 
(731). 
_ 224, HELIANTHUS MULTIFLORUS, L.—Delpino found Helian- 
_ thus fertilised chiefly by Heriades truncorwm, l.., which tapped the 
f lowers in their first (male) stage with its abdomen, and dexterously 
swept up the pollen that exuded from the anther-cylinder with its 
“abdominal collecting-hairs ; hence he concluded that the insect 
and the plant had been specially created for one another. The 
various relations of insects to flowers, as they are described in this 
book, prove such a conception to be untenable. 
I have observed as visitors of H. multiflorus :-— 
_ <A. Hymenoptera—Apide: (1) Megachile centuncularis, F., ep. ; (2) 
iB ictus zonulus, Sm. Siw’ , 8 B. Diptera—Syrphide : (3) Eristalis tenax, L, ; 
Bp eytphus pyrastri, L. ; (5) S. ribesii, L., all three f.p. and s, 
Tribe Anthemidee. 
— 225. AcHILLEA MILLEFOLIUM, L.—This plant is a very heel 
. astance of the advantage of many small flowers being united 
| ster, both for attracting insects and for simultaneous cross- 
ilisation of many flowers by a single insect-visitor. 
\j In the florets of the disk, the corolla consists of a tube scarcely 
nm. long, passing above into a throat 1 mm. long and equally 
de, ending in five triangular teeth. Honey is secreted by an 
ular ridge (0, Fig. 112, 2) surrounding the base of the style, 
