212 Ayinals Entomological Society of America [Vol. IX, 



glandular secretion, instantaneously discharged to the exterior 

 under a high blood pressure which is caused by a muscular 

 contraction, forcing the blood into a specially devised chamber 

 containing the gland cells. It is, therefore, seen that the mem- 

 brane extending across the lumen of the leg plays an all- 

 important part in the discharge of the secretion, because if it 

 were not present the blood would occupy too much space and 

 could not be put under a sufficiently high pressure to stimulate 

 all the gland cells simultaneously. Furthermore, since the 

 nerve and trachea lie in the chamber containing only a few 

 scattered gland cells, this may also be a device for protecting 

 these structures against a high blood pressure. 



FUNCTION OF THE HYPODERMAL GLANDULAR SECRETION. 



On account of the bitter taste, the high volatility and the 

 offensive odor of this secretion, there is no doubt that its 

 primary function is that of protection. Since we know very 

 little about the abiUty of the lower animals to distinguish colors, 

 we can not attribute any protecting significance to the color of 

 this secretion, chiefly because the bright amber color is noticed 

 by a person only when drops are ejected from the femoro-tibial 

 articulations. Since these drops are so inconspicuous, it is 

 doubtful whether they are ever seen by an enemy even as large 

 as a bird. Nevertheless, it is quite probable that the amber 

 color is associated with the taste and odor of the secretion. 



If the bitter taste of the secretion serves as a means for pro- 

 tecting the insect, it must be granted that the animal seizing 

 the insect can taste and that the secretion in stimulating the 

 gustatory organs of the enemy causes an "unpleasant" sen- 

 sation. We are certainly safe in saying that the vertebrate 

 enemies (particularly birds) of this insect experience an offensive 

 gustatory sensation when they attempt to eat these beetles. 

 To say that such a sensation is experienced by its insect enemies 

 can not be emphasized, because it has never been conclusively 

 proved that insects can taste. 



Since we know that insects as a rule have an acute sense of 

 smell and that the higher animals are also endowed with an 

 olfactory sense, we are safe in assuming that the offensive odor 

 of the secretion is sufficient in most cases to guard oiT the 

 enemies of this insect. This statement is supported by the fact 

 that most of the common, strong odors, whether pleasant or 

 unpleasant to us, act as repellents to insects. 



