218 A^inals Entomological Society of America [Vol. IX, 



SUMMARY. 



Hypodermal gland pores are widely distributed over the 

 entire integument of Epilachna borealis. Usually one, but 

 sometimes two pores, lie near the base of almost every hair. 

 Besides lying near the bases of the hairs, the pores on the tarsi 

 and around the femoro-tibial articulations lie in groups. Two 

 groups are located at the extreme proximal end of the tibia and 

 two at the distal end of the femur around the articular mem- 

 brane. All four groups contain 100 pores as an average. The 

 articular membrane contains about 400 pores of another type. 



These beetles always appear wet, and the more they are 

 irritated the wetter they become. The wet appearance is 

 caused by a hypodermal glandular secretion passing to the 

 exterior through the pores. When irritated the beetles eject 

 small drops of the amber-colored secretion from the femoro- 

 tibial articulations through the four groups of pores near the 

 articular membrane and those in the membrane. The discharge 

 of the secretion is accomplished by putting the gland cells under 

 a high blood pressure. This is made possible by a muscular 

 contraction in the femur whereby the blood is forced into a 

 specially devised chamber containing the gland cells which 

 belong to the pores in and near the femoro-tibial articulation. 



The gland cells are of two types. Those with reservoirs are 

 several times larger than those without reservoirs. The former 

 are widely distributed throughout the entire insect, while the 

 latter is found only under the articular membrane of the femoro- 

 tibial articulation. In other respects the two types are alike. 

 Each gland cell has an ampulla and a conducting tube which 

 either runs from the ampulla to the reservoir in the chitin or 

 from the ampulla to the surface of the articular membrane. An 

 efferent tube leads from the reservoir to the surface of the chitin. 



The glandular secretion is bitter and has an offensive odor. 

 Its chief purpose is that of protection, but it probably also aids 

 the beetles in recognizing the different individuals and sexes of 

 the same species. 



