Bacteria' Disease of the Sqnash-hag. 369 



on the part of the insect being a slight sluggishness, a 

 touch causing it to respond actively. An examination 

 of sections made from this individual showed the bacteri;.. 

 in the blood to some extent (see Plate XXVII, Fig 4) 

 but they were apparently quite as abundant in the hypo, 

 dermis. In the adipose tissue there was occasiona.Uy 

 found a small colony of the bacteria; but here there 

 was at the time no general and uniform distribution. 

 From these results it was quite impossible to decide 

 whether the blood became infected by the entrance of 

 germs through the spiracles, or whether there was direct 

 penetration of the hypodermis. The former would seem 

 to be most natural, and 1 am inclined to suppose that 

 the 'fluid of the perivisceral cavity is the seat of first 

 action. On this ground, however, the more marked 

 effect on nymphs, both of squash-bugs and of chinch- 

 bugs would necessarily be explained on a truly physio- 

 logical basis, rather than on the ground of the more 

 penetrable character of the chitinous outer coat. 



TEMPERATURE EXPERIMENTS. 



For a further knowledge concerning the conditions of 

 growth of this bacillus and for a guide to any field ap- 

 plications of the organism, a series of temperature tests 

 was planned, by means of which it was hoped to ascer- 

 tain (1) the period of exposure to various temperatures 

 necessary to kill this organism when mature, and (2) 

 the range of optimum temperature relative to its growth 

 and development. In order to secmre a mature growth, 

 fresh slanting agar tubes wore inoculated, and by means 

 of the water of evaporation the bactei-ia were distributed 

 as much as possible. The tubes were kept at about 80° F. 

 for two days, when the growth was abundant over the 

 w'hole surface, and then the exposures were made as 

 indicated in the table. On last removal from the incuba- 

 tor, other slanting tubes of frosh agar were in a similar 

 way inoculated from these, and the new tubes placed 



under observation for growth developments. 

 24— 



