CONVOLVULACEAE 147 



dependent that its distribution seems to be determined by that of the moth. In 

 some localities the insect is tolerably rare, and pollination being correspondingly 

 infrequent the plant would die out if it did not propagate vegetatively. In this 

 connection Vuyck points out that there are stems of two kinds, the ordinary 

 twining ones, and others that do not twine. The latter are generally lower 

 branches, but they may be produced- higher up, and then grow right down to 

 the ground, sometimes attaining a very great length, and sending out roots here 

 and there. 



Buchanan White says that the convolvulus hawk-moth is rare in England, and 

 that the plant rarely sets fruit. In Scotland, where the moth does not occur, the 

 convolvulus is seldom met with in the wild state. T. H. Corry states that in North 

 Ireland this species is far commoner than C. arvensis, and the convolvulus hawk- 

 moth is comparatively abundant. Hermann MuUer adds that for the area of 

 distribution of the plant to extend somewhat outside that of the moth would be 

 intelligible, as there are other insects that play the part of pollinators, though to 

 a subordinate degree. 



The hawk-moth in question has been observed by Delpino (Florence), Herm. 

 Miiller (Westphalia), Alfken (Bremen), and Knuth (Kiel). Herm. Muller (H. M.) 

 and Buddeberg (Budd.) add the following list. — 



A. Coleoptera. NitiduUdae: i. Meligethes sp., uncommonly numerous, 

 po-dvg. and forcing its way into the nectar-passages (H. M.). B. Diptera. 

 \a) Empidae: 2. Empis sp., inserting its proboscis into the nectar-passages (H. M.); 

 3. E. tessellata F., skg. (H. M.). (fi) Syrphidae: 4. Rhingia rostrata Z., skg. and 

 po-dvg. (H. M.). C. Hymenoptera. Apidae : 5. Chelostoma nigricorne Nyl. 5, 

 freq., skg. (H. M.) ; 6. Halictus cylindricus F. S, do. (H. M.) ; 7. H. zonulus Sm. 5, 

 po-cltg. (H. M.) ; 8. Megachile centuncularis L. S, skg. (H. M.) ; 9. Stelis aterrima 

 Pz. t, do. (Budd.). D. Thysanoptera. 10. Thrips, very numerous (H. M.). 



Vuyck gives the following list of species (determined by Ritzema). — 



A. Hymenoptera. Apidae: i. Bombus terrester Z. 5 ; 2. B. hypnorum Z. $; 

 3. B. agrorum F.'^; 4. Megachile centuncularis Z. 5; 5. Halictus cylindricus F. 5; 

 6. Vespa rufa Z. J- B. Diptera. (a) Syrphidae: 7. Eristalis tenax Z. 5 and J; 

 8. E. arbustorum Z. J ; 9. E. horticola Deg. 5; 10. Syrphus balteatus Deg. S and 5; 

 U.S. ribesii Z. S and 5 ; 12. S. pyrastri Z. § ; 13. S. corollae ^. $ ; 14. Helophilus 

 pendulus Z. 5; 15. Rhingia campestris Mg. 5. (3) Empidae: 16. Empis livida Z. 

 S and 5. (c) Muscidae: 17. Sarcophaga albiceps Mg.i; 18. Lucilia cornicina 

 Fabr. S; 19. Anthomyia sp. 5. 



The humble-bees mentioned, especially Bombus agrorum F., play a considerable 

 part in pollination, which is also effected by the po-dvg. hover-flies, though these 

 usually bring about autogamy. The remaining insects, to which the earwig 

 (Forficula auricularia Z.) may be added, are unbidden guests. 



The following were recorded by the observers, and for the localities 

 stated. — 



Knuth (Kiel), the beetle Meligethes as an unbidden guest. MacLeod (Flanders), 

 2 hover-flies, an Empid, and a short-ton^ed bee (Bot. Jaarb. Dodonaea, Ghent, vi, 

 1894, p. 371)- Scott-Elliot (Dumfriesshire), 2 humble-bees and an Empid ('Flora of 

 Dumfriesshire,' p. 120). Ducke (Trieste), the bee Eucera (Macrocera) malvae 

 Rossi. 



