Robertson — Flowers and Insects. 447 
occur early, there is provision for spontaneous self-pollina- 
tion, for by the closing of the petals at night, or in cloudy or 
rainy weather, the anthers of some of the longer stamens 
come in contact with the stigmas. 
The flowers are pollinated by bees principally of the genus 
Andrena. On April 10th and 11th, I noted as visitors : — 
Hymenoptera — Apidae: (1) Apis mellifica L. abe i re eri ¢ 
Bombus arte Cr. 9; (8) Ceratina dupla Say SF dnivntae (4) 
Andrena sayi Rob. ff, freq.; (5) A. salicis Rob. 9; (6) A. pean 
Rob. 2; (7) ne cressonii Rob. ¢'@; (8) A. poles or Sm. ('Q, 
(9) A. rugosa Rob. (J; (10) A. forbesii Rob. 9, freq.; (11) A. mariae Reb, 
d'; (12) A. claytoniae Rob. ¢/; (13) Halictus winttils Rob. @; (14) 
pilosus ci ie (15) H. zephyrus Sm. 9; (16) H. caeruleus Rob. 9 ; dat 
H. confus re Sabo H. stultus Cr. 9 —all sucking; Tenthredinidae: 
(19) ct arvensis Sa 
on wecaus ae: (00) Mesograpta marginata Say; (21) M. Nr ree 
y; (22) Sphaerophoria cylindrica Say; (23) Eristalis aeneus F.; 
sats (24) Phorocera edwardsii Will.; Muscidae: (25) Loui conta 
F. — all sucking. 
Review OF THE PRECEDING Rosacear: —In table I the 
plants are given as nearly as practicable in the order in which 
they were observed, beginning with those blooming first. 
Little needs to be said of Geum vernum and Rubus occidentalis, 
which are sparingly visited by insects. 
Spirgea aruncus strikes us as the most peculiar, since it 
shows a strong preponderance of Coleoptera. Beetles occur 
on nine species, but are not very important except in case of 
Spiraea. 
Four species show a strong preponderance of bees. These 
are Pyrus coronaria, Rubus villosus, Rosa humilis and 
setigera. These are large flowers, forming a firm support for 
heavy insects, and requiring large insects readily to pollinate 
them. The two former have the nectar more deeply con- 
cealed than usual, so that it is only accessible to long tongues. 
The Andrenidae which I noted on Rubus villosus were only 
collecting pollen. The roses have no nectar, but yield abun- 
dant pollen, and are the largest and most attractive of all the 
flowers. These four species may be regarded as humble-bee 
flowers, though they are also less frequently visited by other 
large bees. 
