PRIMULACEAE 69 



in which this was purple -violet, except for its star -shaped yellow centre and 

 sometimes whitish margin. 



Visitors. — I saw at Kiel (25. 4. '95) several individuals of Bombus hortorumZ. 5, 

 flying busily from flower to flower, and sinking their proboscis into the corolla-tube, 

 so that in long-styled flowers the laciniae, and in short-styled ones the head became 

 dusted with pollen. This was then transferred to stigmas at corresponding levels, 

 and legitimate crossing regularly effected. These humble-bees, however, not only 

 visited this species, but also P. officinalis and P. elatior, which were growing near, 

 so that a great deal of hybridization as well as crossing must have been brought 

 about. In some cases the bee Anthophora pilipes F. 5 behaved in the same way 

 as Bombus hortorum, though it preferred the flowers of Pulmonaria officinalis, 

 which grew close by. 



In the two last-named insects the proboscis is 18-21 mm. long, so that it 

 can easily reach the nectar concealed in the bases of the flowers of this and the 

 last two species. The average length of the corolla-tube is here 20 mm., but 

 in P. officinalis and P. elatior it is considerably shorter. As a bee when sucking 

 can completely thrust its head (about 5 mm. long) into the opening of the corolla- 

 tube, it follows that other species with shorter tongues are able to legitimately 

 pollinate P. officinalis and P. elatior. Hermann Miiller actually observed humble-bees 

 of the kind doing this. 



The three species of Primula in question can also be pollinated by the brimstone 

 butterfly (Rhodocera rhamni Z.). Cobelli saw it on P. vulgaris, Mulberger and 

 Hermann Miiller on P. elatior, and myself on all three (26. 4. '96). 



Cobelli also observed Bombylius medius Z. on P. vulgaris, and the other two 

 species of Primula are also visited by Bombyliids, though only those with a par- 

 ticularly long proboscis are able to get at the nectar. 



On March 21, 1896, I saw Vanessa urticae Z. flying persistently from flower 

 to flower of this species (eighteen were successively visited). This butterfly sucked 

 very vigorousl}', and evidently succeeded in getting a part of the nectar. Though 

 useless to the short-styled flowers, it undoubtedly transferred their pollen to the 

 stio-mas of long-styled ones. I also saw the honey-bee visit several flowers in 

 succession, and as it sucked with equal zeal it perhaps succeeded in reaching 

 the uppermost layer of nectar. 



Wiistnei noticed the bee Anthophora acervorum Z. in the island of Alsen, and 

 Cobelli saw small beedes, though these could only effect crossing by accident. 



We may say of Primula vulgaris, P. elatior, and P. officinalis, that all three are 

 chiefly pollinated by long-tongued Hymenoptera and the brimstone butterfly, while 

 Bombyliids, Vanessa urticae, and the honey-bee are visitors of secondary importance. 



I was able to observe directl}' the transfer of pollen by visitors for the short 

 distance of a few metres, but Focke has seen a hybrid between P. vulgaris and 

 P. officinalis, for the development of which it must have been carried a kilometre. 



Gibson (' Flora of St. Kilda ') states that in St. Kilda, the most westerly island 

 of Scodand (except the barren Rockall), where bees, wasps, and Lepidoptera are 

 absent, the primrose appears to be pollinated by flies, for fruits are now and then set. 



Archer Briggs (Rep. Inst., Plymouth, iv, 1871-2) did not notice the larger 

 humble-bees in England, but only Anthophora acervorum Z., freq., smaller bees 



