288 Chemotropic Responses of Insects 



and cane molasses — the latter itself being an important attractive agent. 

 Two small American balloon traps were fitted up for the purpose and 

 were suspended close together from the same tree. The one trap A was 

 charged with 60 c.c. beer solution and the other trap B was charged 

 with 30 c.c, undiluted beer and 30 c.c. of a 25 per cent, solution of cane 

 molasses, with the following results. July 13-14. Trap A, 11 flies; 

 B, 11 flies. July 14-16. A, 4 flies; B, 57 flies. July 16-19. A, 5 flies; 

 B, 65 flies. It was observed that Diptera responded much more quickly 

 to the stimulus of beer, but the latter speedily lost its attractive pro- 

 perties. After the second day, probably on account of the fermenta- 

 tion which was going on in the molasses mixture, trap B became far 

 more attractive. On July 6-8, 200 c.c. of a 50 per cent, solution of beer 

 in a Minnesota trap attracted 928 Diptera, the largest number recorded 

 in any of our experiments. On July 11-13 a 33 per cent, solution of 

 beer attracted 175 Diptera. The species attracted are recorded below, 

 the figures in brackets referring to the weaker solution. Scatopse sp. 11*. 

 Rhyphus punctatus Fab. 98cJ, 60?, 27* (5(J, 2$). R. fenestralis Scop. 

 2$. Onesia sepulchralis L. 20c^, 12$ {iS, 6$), Sarcophaga carnaria L. 

 2c?, 6? (5(J, 1$). Pollenia rudis Fab. 8^ (2c?, 5$). Muscina stabulans 

 Fall. 1(?. Morellia hortorum Fall. Ic?, 1$. Mesembrina meridiana L. 

 8(J, 3$ (2c?). Pyrellia eriopthalma Macq. 8c?, 10? (1$). Calliphora ery- 

 throcephala Mg. 29(?, 24? (3c?). C. vomitoria L. 6c?, 3? (1 ?). Euphoria sp. 

 1?. Lucilia sp. 12(?, 8?. Mydaea medifabunda F. 4(?, 1? (1(?, 2?). 

 M. impuncta Fall. 23c?, H? (6c?). Spilogaster duplicata Mg. 3?. S. pvb- 

 escens Stein. 3c?. S. demigrans Ztt. (Ic?)- Hydrotaea dentipes Fab. 7c?, 

 1? (1*). Hylemyia strigosa Fab. 92c?, 30? (37c?, 44?). Polietes lardaria 

 Fab. 3c?, 8? (Ic?). Hytodesia marmorata Ztt. 2?. Anthomyia pluvialis L. 

 1?. Fannia canalicularis L. 7c? (2c?). F. manicata Mg. Ic?. Fannia sp. 

 17c?, 5*. Scatophaga stercoraria L. 16c?, 2? (5c?, 10?). Themira putris L. 

 Ic?. T. minor Hal. Ic?, 7?. Drosophila obscura Fall. 2*. Dolichopus 

 griseipennis Stan., Piophila vulgaris, P. nigriceps Mg., a few examples of 

 each were attracted by the 50 per cent, solution and many examples of 

 a species of Sciara and Sepsis. Helomyza sp., a few examples were at- 

 tracted by both solutions. Unidentified Diptera (mostly Anthomyidae) 

 300 (32). 



(12) Cane tnolasses. The variety used was that commonly known as 

 "black treacle " — an extremely complex substance of variable chemical 

 composition. Our researches have not so far included an investigation 

 of the attractive agents present, but it is intended to pursue this line 

 of research at the earliest opportunity. Cane molasses (50 c.c.) was used 



