THE AMERICAN ENTOMOLOGIST. 



289 



EXPERIMENTS WITH YEAST FERMENT ON 

 VARIOUS INSECTS. 



[Among the various experiments which 

 we have had made with Yeast Ferment as 

 an insecticide, during the present year, 

 the following from two well known ob- 

 servers will prove of interest. — Ed.] 



EXPERIMENTS BY PROF. J. E. WILLET, OF 

 MACON, GA. 



The Cotton-worm [Aletia argillacea) 

 made its appearance in this State late in 

 the summer, and not in large numbers. 

 The first reported to me appeared in Mitch- 

 ell County, near the line of Georgia 

 and Florida, August 31st. From the pre- 

 valence of the great gale of that date, no 

 experiments were attempted with that 

 brood. The following experiments were 

 made with larvae of the next brood. 



In the experiments made by me, last 

 year, it was observed that the cotton 

 leaves which had been sprinkled with 

 beer and yeast and were fed to the cotton- 

 worms in confinement, adhered together, 

 when the larvae " webbed up " in them 

 and remained moist and liable to mould. 

 This was suspected to be one cause of the 

 great mortality in the larvae and pupae. 

 To guard against this the beer, in the 

 following experiments, was made with 

 much less sugar, and the yeast was more 

 diluted. Both, however, were very active 

 and were full of the fungus cells. 



September 20th, one hundred and fifty 

 larvae, about half-grown, were selected and 

 placed in three suitable boxes, fifty larvae 

 in each box. Those placed in the first 

 box were supplied, from time to time, with 

 fresh cotton leaves sprinkled with beer ; 

 those in the second box with cotton leaves 

 sprinkled with flour yeast ; and those in 

 the third box with leaves sprinkled with 

 water. The last served as a basis of com- 

 parison with those fed on the beer and 

 yeast ferment. 



September 2gth, all the living had webbed 

 up, the larvae having fed on the sprinkled 

 leaves from five to nine days. October 

 19th the last moths emerged. The long 

 delay in the pupa state was doubtless 



owing to the prevalence of a cold north- 

 easter. They were kept in confinement 

 till October 27th, to permit the escape of 

 any parasites from the pupae. None have 

 been seen. As the larvae were taken from 

 the field, when two or three days old, and 

 were fed in confinement until those for ex- 

 periment were selected, there was probably 

 no opportunity for attack from insect 

 enemies. 



The leaves were not disturbed while the 

 larvae were webbing ; fresh cotton limbs 

 being simply laid on those, in which the 

 worms were spinning. When all the worms 

 had pupated, the old leaves containing 

 most of the pupae were found to be damp 

 and mouldy, especially those which had 

 been wetted with beer and yeast. The 

 leaves therefore were separated, and the 

 pupae were carefully removed and placed 

 on cotton batting in smaller paper boxes. 



The mortality was as follows : of those 

 fed on leaves sprinkled with water and 

 with beer, none died in either the larva 

 or pupa stage. One moth from the larvae 

 fed on beer was imperfect, and did not 

 fully expand its wings. Of the larvae fed 

 on cotton sprinkled with yeast, two larvse 

 and three pupse died, or about ten per 

 cent. 



Last year, the greatest mortality occurred 

 among the larvae fed on beer ; this year 

 there were no deaths in connection with 

 the beer. The beer had an excess of sugar, 

 which when applied to the leaves rendered 

 them very sticky. This was remedied this 

 year by the use of less sugar. The same 

 result was attempted in the case of the 

 yeast by dilution ; but the success was in- 

 complete, by reason of the imperfect solu- 

 bility of the gluten, dextrine and other 

 constituents of the fermenting flour. Even 

 when much diluted with water, the yeast 

 coated the leaves with a white film, which 

 resisted most successfully the action of 

 rain and dew. 



From its greater fluidity and hence 

 a more general action and reaction, we 

 should expect the beer to contain a greater 

 number of yeast germs, and to be more 

 potent in its effects than yeast. 



