16 BULLETIN 828, U. S. DEPARTMENT OF AGRICULTURE. 



WINTER TRANSMISSION OF WILT. 



BEETLE HIBERNATION EXPERIMENTS. 



As previously reported, 1 in some cases, at least, striped cucumber 

 beetles are capable of carrying the wilt organism during six weeks' 

 artificial hibernation in cold storage. Several similar cold-storage 

 tests have been carried out since that report. Striped beetles both 

 of the hibernating and summer broods were used, and the conditions 

 of temperature and humidity were varied in different sets. How- 

 ever, in no case have we been able to keep the beetles alive for a 

 longer period than six weeks. 



Experiments of 1916. — It was thought possible that better success 

 might be obtained if the beetles were allowed to hibernate under 

 more natural conditions. Accordingly, in eastern Long Island during 

 September and early October, 1916, about 4,000 cucumber beetles 

 (mostly Diabrotica vittata) were collected, and 150 to 300 were intro- 

 duced into each of 20 large wire-covered cages (PL II, fig. 2). These 

 cages were 4 feet cubes, were provided with solid board bases with- 

 out bottoms, and were set 15 inches into the soil. A pile of dry 

 sticks and chips was placed in one corner of each cage, and the 

 imprisoned beetles were fed upon wilted cucumber and squash vines 

 until the 1st of November, at which time settled cold weather had 

 come and all the beetles had disappeared from view. 



This experiment was duplicated the same fall at Giesboro Point, 

 D. C, using about 2,500 striped and 12-spotted cucumber beetles, 

 the two species being caged separately. From 50 to 150 beetles 

 were introduced into each of 15 cages provided in this case with a 

 double covering of wire netting and fine cheesecloth. Boxes filled 

 with hay or excelsior were placed in part of the cages and in a few 

 cages a pile of dry chips, sticks, and bark was also added. 



In the following spring cucumbers were planted in the cages in 

 both localities, and the plants were kept under careful observation 

 from the first appearance of warm weather until cucumber beetles 

 had long been present in the surrounding fields. In all this time 

 not a single cucumber beetle nor a beetle-injured leaf was found 

 inside any of the 20 cages on Long Island or of the 15 at Giesboro 

 Point, D. C. 



During September, 1916, a supplementary test was started, using 

 11 pint glass jars with 2 inches of fine leaf mold in the bottom and 

 covered at the top with fine cheesecloth. From 18 to 50 cucumber 

 beetles were placed in each of these jars, fed upon wilted cucumber 

 plants, and kept over winter in an open shed. Many of the beetles 

 were still alive 38 days after imprisonment, but in the spring fol- 

 lowing all were dead. 



i Rand, P. V., and Enlows, Ella M. A., 1916. Op. cit., p. 417. 



