PART III. | THE MECHANISMS OF FLOWERS. 495 
of the under lip, and with its mid and hindfeet to the two lobes 
of the under lip; then, if its proboscis is not less then 10 mm, 
long, it can at once reach the base of the flower. While sucking, 
the thorax, and in the case of small workers the base of the 
abdomen also, fills up the space between the upper and lower lips, 
and the vaulted upper lip fits the bee’s back, which is pressed 
against the stigma and the open face of the anthers. These 
organs are often rubbed also by the bee’s head as it enters the 
flower. In either case, the lower stigma gets touched before the 
anthers, and as the bees fly diligently from flower to flower, cross- 
fertilisation proceeds regularly. 
The following observation shows how much this plant is visited 
by humble-bees in fine weather. One fine spring morning (May 
17, 1868), while I was watching Bombus agrorwm feeding on 
Lamium album, I observed that by the expansion and contraction 
of the bee’s abdomen each separate act of sucking could be 
distinguished ; and that it was possible to tell, when a bee began 
to suck, whether the flower was already exhausted of its honey. 
I found that between 9 and 10 A.M.a bee of the species Bombus 
agrorum abandoned four to five flowers on an average after a 
single taste before it found a flower on which it performed the act 
of sucking several (four to six or even eight to ten) times. By 
that early hour of the day four-fifths of all the flowers of this 
plant had been emptied of their honey. 
Visitors : Hymenoptera—A pide : (1) Bombus agrorum, F. $ 2 (10—15) ; 
(2) B. hortorum, L. § 2 (18—21); (3) B. silvarum, L. 9 (12—14) ; (4) B. 
senilis, Sm. 9 (14—15); (5) B. lapidarius, § 9 (10—14); (6) B. Scrim- 
shiranus, K. 2 § (10), creeping far into the flower; (7) B. Rajellus, Ill. @ 
(12—13) ; (8) B. pratorum, L. 9 (11—12), all sucking normally, and sometimes 
brushing pollen off their backs into the pollen-baskets ; (9) B. terrestris, L. 
2 (7—9), bites through the tube close above the calyx in open flowers and in 
nearly mature buds; (10) Apis mellifica, L. 8 (6), only reaches the honey 
through holes bitten by B. terrestris; (11) Anthophora pilipes, F. 9 ¢; 
(12) Eucera longicornis, L. ¢ (10—12); (13) Melecta armata, Pz. 2 (124), 
the last three sucking normally; (14) Andrena nitida, K. ? (33), s., 
through the holes bitten by B. terrestris ; (15) Andrena albicans, K. 9 ; (16) 
Halictus levigatus, K. 2. I saw these last two collecting pollen ; they seemed 
as likely to effect self-fertilisation as cross-fertilisation. B. Diptera—Syrphide : 
(17) Rhingia rostrata, L., creeps a little way into the flower and inserts its 
tongue, without touching either stigma or anthers. See also No. 590, IIL., 
and No. 609. 
t Leonurus Cardiaca, ., is visited by the hive-bee and by 
| humble-bees (590, 11. ; 6009). : 
