NO. l8 SENSE ORGANS OF COLEOPTERA — McINDOO 59 



unicellular glands distributed over the entire body surface. In fact 

 this type of scent organ is the only one in lady-beetles known to the 

 writer. The bean beetle, like other coccinellids, is well supplied with 

 these glands. All parts of the body surface are covered with com- 

 paratively large hairs. Near the base of each hair there is usually one 

 and sometimes two gland pores (figs. 6, lO, 14, 15, 17-19, Po). The 

 large gland cells (figs. 10, C, and 15, A, GC) are variously con- 

 structed, but are always connected with reservoirs lying in the integu- 

 ment. In some of the smaller appendages, for example the maxillary 

 palpi, where the available space is limited, the gland cells lie some 

 distance from their pores and often nearly fill the lumen of the 

 appendage. 



The writer (42) in 1916 reviewed the literature on reflex " bleed- 

 ing " in beetles and added ^further information by using the squash 

 lady-beetle, EpilacJuia horcaVis. When disturbed certain coccinellid 

 and meloid beetles fold the antennae and legs against the body, eject 

 small drops of liquid from the femoro-tibial articulations, and feign 

 death. There has been a controversy as to how the liquid is expelled 

 so quickly and as to whether the liquid is blood or is a glandular se- 

 cretion. The writer has now shown that in regard to the squash lady- 

 beetle and the Mexican bean beetle {R. corriipta) the phenomenon is 

 a true reflex, but that instead of the licjuid being blood, it is a secretion 

 from two types of hypodermal glands and that it passes to the exterior 

 through innumerable tubes opening near and in the articular mem- 

 brane. The gland pores of the first type, with reservoirs, lie in groups 

 on the tarsi and around the femoro-tibial articulations. Two groups 

 of these are located at the extreme proximal end of the tiliia and two 

 at the distal end of the femur around the articular membrane (fig. 19, 

 A, Po). The gland pores of the second type, without reservoirs, lie 

 in the articular membrane, marked a in figure 19. The discharge of 

 the amber-colored secretion is accomplished by putting the gland cells 

 under a high blood pressure. This is made possible by a muscular con- 

 traction in the femur whereby the blood is forced into a specially de- 

 vised chamber containing the gland cells which belong to the pores in 

 and near the femoro-tibial articulation. The glandular secretion is 

 bitter and has an offensive odor. Its chief purpose is that of pro- 

 tection, but it probably also aids the beetles in recognizing the different 

 individuals and sexes of the same species. 



Hollande (26) in 191 1 wrote a large pai)er in which he reviewed 

 the literature on the phenomenon of discharging "blood " in insects 

 and on the toxicity of this sul)stance. He also added new information 

 on these subjects. He reports that self-bleeding has been found in 



