38o ANGIOSPERMAEDICOTYLEDONES 



secrete abundant nectar ; they are consequently much sought by numerous insect? 

 particularly bees, which bring about cross-pollination and also lead to the formatioi 

 of the numerous hybrids. 



Kerner states that the 5 flowers of many species (e. g. S. fragilis Z., S. viminali 

 Z., S. triandra Z., and S. purpurea Z.) mature earlier than the t flowers of adjacen 

 -trees. Jordan says that the anthers turn their pollen-covered surfaces towards the sid 

 in such a way that the proboscis of an insect inserted between the stamens to sue 

 nectar must be thickly dusted with pollen. Heinricher, von Seemen, and other 

 observed androgynous inflorescences. 



One of three androgynous inflorescences of S. Caprea Z. examined by Heinriche 

 bore mixed S and 5 flowers at the base, and only J on the upper half; the secori' 

 bore only $ at the base, only J at the top, and both $ and j in the middle; th 

 third bore only 5 flowers. 



As insect visitors go from one species of willow to another indiscriminately, it' 

 difficult to assign them to individual species. In the following lists, therefore, th 

 visitors of various species are often grouped together, as was done by Hermani 

 Miiller. 



othecin 



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2576. S. cinerea L. ; 2577. S. Caprea L. ; 2578. S. aurita L., and o\}a&^ 

 (Herm. Miiller, 'Fertilisation,' pp. 524-5, 'Weit. Beob.,' II, pp. 210-11 

 ' Bloemenbiol. Bijdragen.') 



Visitors. Burkill observed the following on the Yorkshire coast (' Fertilisatioi 

 of Spring Flowers '). 



A. Diptera. (a) Muscidae : i. Scatophaga stercoraria Z., on J and 5 catkin? 

 skg. (h) Stratiomyidae '. 2. Lasiopa sp., as i. po-cltg. (r) Syrphidae-. 3, Eristali 

 arbustorum Z., on J catkins ; 4. Melanostoma quadrimaculata Verral, on 5 catkin; 

 skg. B. Hymenoptera. Apidae : 5. Andrena gwynana K., on $ catkins, sk^ 

 and po-cltg. ; 6. Apis mellifica Z., on J and 5 catkins, very common, skg. ; 7. Bombu 

 agrorum Z'., on $ catkins, skg. ; 8. B. terrester Z., on S and j catkins, skg. 



Krieger observed the following bees on S. Caprea at Leipzig. 



Apidae : i. Andrena albicans Afiill. ; 2. A. cineraria Z. a J ; 3. A. eximia Sm. 

 4. A. extricata Sm.) 5. A. flavipes Pz.; 6. A. gwynana K.', 7. A. nitida Fourcr. 

 8. A. ovina Klug.\ 9. A. parvula K.\ 10. A. tibialis K.\ 11. Bombus derhamellu 

 K. $ (=B. rajellus ZT.); 12. B. hortorum Z. 5; 13. B. terrester Z. ; 14. Collete 

 cunicularius Z. ; 15. Halictus calceatus Scop. (=H. cyHndricus F)\ 16. H. \t\\ 

 Z%j. 5 ; 17. H. nitidiusculus Z'. ; 18. Nomada lineola/*a. ; 19. Osmia rufa L.t 

 20. Podalirius acervorum Z. S, freq. ; 21. Psithyrus quadricolor Lep. a $. 



Herm. Miiller gives the following list for the 3 species. 



A. Coleoptera. (a) Elateridac. i. Corymbites castaneus Z. ; 2. Limoniu 

 parvulus Pz. {d) Nitidulidae : 3. Meligethes sp., freq., nect-lkg. B. Diptera 

 \a) Bibionidae : 4. Bibio johannis Z., skg. ; 5. B. marci Z., do. ; 6. Dilophus vulgari 

 Mg., freq. (<5) Bombyliidae : 7. Bombylius major Z., skg. {c) Conopidae : 8. Myop 

 buccata Z., not infreq., skg.; 9. M. testacea Z., do.; 10. Sicus ferrugineus Z., d( 

 {d) Empidae: 11. Empis sp., freq., skg.; 12. Rhamphomyia sulcata Fall., skj 

 \e) Muscidae'. 1 3. Calliphora erythrocephala J:^., skg. ; 14. Exorista sp. ; 15. Goni 

 ornata Mg., skg.; 16. Pollenia rudis F., po-dvg. ; 17. P. vespillo F., skg. an 

 po-dvg. ; 18. Scatophaga merdaria Z., freq., skg.; 19. S. stercoraria Z., A 

 (y) Syrphidae: 20. Brachypalpus valgus Pz., skg. and po-dvg.; 21. Cheilosi 

 brachysoma Egg., do.; 22. C. chloris Mg., do.; 23. C. modesta Egg., da 



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