1916] Reflex '' Bleeding" of Epilachna 211 



place. When a tactile hair is touched, its sense cell is stim- 

 ulated. Since the sense cells lie near and sometimes against the 

 gland cells, the former may in some unknown way stimulate 

 the latter. If such should be the case, then the gland cells 

 would begin vigorously at once to produce more secretion. 

 And as a result much more liquid would be discharged than 

 ordinarily. If such a relation exists between the gland cells 

 and tactile hairs, the writer can think of no simple reflex better 

 adapted for protecting the insect. 



Considering the discharge of liquid at the femoro-tibial 

 articulation, there is no question about the reflex, but whether 

 the stimulus is brought about by pressure on the chitin or by a 

 stimulation of several sense cells belonging to tactile hairs, is an 

 open question. Since only a slight mechanical irritation at the 

 distal end of the femur is required to cause a discharge of the 

 secretion, it is more reasonable to think that the stimulation 

 is brought about by the tactile hairs than by the pressure on 

 the chitin. As soon as the tactile hairs are touched, the muscles 

 contract folding the tibia against the femur and forcing the 

 blood into the chamber containing the gland cells. At once 

 the gland cells are put under a high blood pressure which 

 immediately stimulates them. Instantaneously they discharge 

 all the secretion in their ampullae causing the secretion in the 

 reservoirs to be shot to the exterior. Now the gland cells 

 without reservoirs play their part by immediately increasing 

 the size of the drop of discharged liquid. Causing drops to be 

 discharged may be continued until the gland cells become 

 exhausted which really occurs after the fifth or sixth drop has 

 been expelled. Each drop is smaller and is discharged less 

 quickly than the preceding one. This shows that the supply 

 of Hquid is limited from the beginning, and that a Httle more 

 time is required for producing each succeeding drop than the 

 preceding one, but if the liquid were blood such would not be 

 the case. It would seem that the liquid secreted under such an 

 emergency would not be exactly the same in composition as 

 that which is produced when the cells are not overworked, but 

 under normal conditions it is perhaps never necessary for these 

 insects to exhaust this glandular secretion. 



From the preceding it is evident that the phenomenon of 

 ejecting liquid from the femoro-tibial articulation is a true 

 reflex, but instead of the hquid being blood, it is a hypodermal 



