574 NEW JERSEY AGRICULTUEAL COLLEGE 



If the bogs have water enough to cover completely but not enough 

 to reflow, another method must be adopted. Under no circumstances 

 should the bogs be uncovered until after April 15th if yellow-head 

 injury is to be averted. If the season is late and early April is cold, 

 even that is too early, and April 25th to May 1st is safer. If the 

 black-head (Eudemis) is also to be guarded against, dates should 

 be less depended upon, and the temperature of the water gives the 

 safest guide. Two weeks after 59° or 60° is recorded at two feet in a 

 quiet part of the pond, i. e., not in a direct current or near the gates, 

 it will be safe to draw. That will usually bring it to the first week 

 in May, and if an arbitrary date is desired May 10th will be more 

 often right than wrong. 



If it be desired to draw earlier and slowly, that can be done by a 

 double gate to take off the water from the lower levels first. The 

 accompanying sketch is self-explanatory, and shows in sections how 

 the water enters at the bottom of an inner solid plant wall into a com- 

 partment closed at the bottom and opened at top for the overflow. 

 This outer wall is made up of planking in the usual way, and the 

 scheme leaves the warm upper layers, bringing the vines gradually 

 under the influence of the higher temperature and causing the collapse 

 of any eggs that may yet remain sound at lower depths. 



OBSERVATIONS ON RE FLOWING. 



In the preceding recommendations it is assumed that reflowing the 

 bogs is a certain remedy in all cases, provided the water is kept on 

 the bogs at least twenty-four hours and provided all the larvae are 

 hatched. In ordinary cases this assumption seems to be warranted. 

 It is certain that I have seen bogs reflowed and completely cleaned 

 where there had been caterpillars in great plenty before. It is also 

 certain, from direct experiment, that pupEe are nearly as much affected 

 by the water covering as the larvae, and this was proved by a simple 

 laboratory experiment. 



July 19th, pupae of the Eudemis were submerged in vials filled with 

 water. No, 1 contained two pupse, which were left covered forty-six 

 hours, and were then transferred to a dry vial carefully kept from jars. 

 Nos. 2 and 3 contained two pupje each, which were left covered sixty- 

 five hours and then dealt with as before. The five remaining pupas 



