14 BULLETIN 75, U. S. DEPARTMENT OF AGRICULTURE. 



MOTHS AND OTHER NIGHT-FLYING INSECTS. 



Owing to the fact that tripped flowers are sometimes abundant 

 while day-flying insect visitors are scarce, it was suspected that night- 

 fljing insects might be a factor. To secure information on this point 

 two series of experiments were undertaken. 



One of these experiments was conducted at Pulhnan, Wash., in 

 1909. Seven alfalfa plants were inclosed in fine-meshed mosquito 

 netting. Five of the plants were left under the netting during the 

 entire time of the experiment in order to find out what proportion 

 of the flowers become tripped when insects were entirely excluded. 

 Two of the plants were kept inclosed in netting during the daytime, 

 but were uncovered during the night. The results obtained are 

 given in Table V. 



Table V. — Alfalfa fiowers tripped hy night-flying insects at Pullman, Wash., 1909. 



On plants inside of netting. 



On same plants outside of 

 netting; open to insects. 



Plant. 



Flowers 

 tripped. 



Flowers 



bearing 



pods. 



Plant. 



Flowers 

 bearing 

 pods. 



No. 11 -. 



Per cent. 



*o 



*0 



*3.92 



*3.03 



*o 



t4.63 



t4.60 



Per cent. 

 *1. 16 



*.o 



*8.57 

 *2.59 

 *1.36 

 t5.78 

 t2.51 



No. 11 



Per cent. 

 37.31 



No 12 . - .. 



No 12.. 



16.12 



No 14. . . • 



No. 14.. 



56.60 



No. 15 



No. 15 



20.51 



No. 17 



No. 7 



35.38 





No. 10 



30.35 



No. 10... 











* Inclosed in netting during entire e.xperiment. f Inclosed in daytime; open for night-flying insects. 



A similar experiment was conducted at Chico, Cal. On May 31, 

 1909, 400 alfalfa flowers on several difl'erent plants were marked and 

 observed until June 2. Table VI shows how many flowers were 

 tripped during the day or night. 



Table VI. — Alfalfa flowers tripped during different periods of the day and night at Chico, 



Cal, 1909. 



Period covered. 



Number 

 of flowers 

 tripped. 



Period covered. 



Number 

 of flowers 

 tripped. 



From— 



To— 



From— 



To- 



4 p. m., Mar 31 



7.30 p. m., May 31... 



5.30 a. m., June 1 



10 a.m., June 1 



7.30 p. m., May 31. 

 5.30 a. m.j Junel.. 



10 a. m., June 1 — 



11 a.m., June 1 



22 

 

 23 

 11 



11 a. m., June 1 



2p. m., June 1 



4 p. m., Junel 



7.30 p.m., June 1... 



2 p. m., Junel 



4 p. m., June 1 



7.30 p.m., Junel.. 

 a.m., June 2 



10 

 18 

 18 

 



From the evidence presented in the two preceding tables, as well as 

 from the results of observations made at other times and places, it is 

 clear that night-fljdng insects are at most a small factor in tripping 

 alfalfa flowers. I 



