1963 ] Eisner, Hurst and Meinwald — Defense Mechanisms 1 1 1 
that its rear was pushed into the sand, proceeded to eat it head first 
(Plate ii, fig. 3). Under these conditions most, if not all, of 
the secretion must have been ejected into the sand, sparing the mouse 
itself. The mouse betrayed no signs of discomfort and both beetles 
offered were devoured almost entirely. Only the legs and wings were 
discarded, as well as the tips of the abdomens, which presumably still 
contained the gland reservoirs. One might add that this same mouse, 
and others of the same species, have been seen to overcome and eat tene- 
brionid beetles of the genus Eleodes in exactly the same fashion (Eis- 
ner, 1960b, and unpublished). Eleodes, like Chlaenius, also sprays 
from the tip of its abdomen, although its secretion contains quinones 
rather than a phenol (Blum and Crain, 1961 ; Chadha et al., 1961b). 
2. Versus Abacion. 
The single millipede offered was promptly severed midway by the 
mouse’s first bite. The mouse retreated instantly, scurrying about the 
cage with its muzzle intermittently pushed in the sand. Within sec- 
onds it returned to bite the millipede again, only to be repelled tem- 
porarily as before. This sequence of attack and retreat was repeated 
several times, until the mouse finally grasped several multisegmented 
portions of the millipede and ate them one by one. But most of the 
millipede was left uneaten. A strong odor of p-cresol permeated the 
cage. Grasshopper mice are known to pursue their prey relentlessly 
even in the face of repellent secretions (Eisner et al., 1961 ; Egoscue, 
i960), and the persistent aggressiveness evidenced in this encounter 
was in no way unexpected. 
IV. Irritant Effectiveness of the Secretions and Their Phenols. 
The chemical evidence has shown (part II, above) that m-cresol 
and />-cresol are not the only components of the secretions. The pos- 
sibility therefore exists that the unidentified lesser components 
contribute in an important way to the overall effectiveness of the 
secretion. Such possibility would not be without real precedent. For 
instance, the spray of the whipscorpion, Mastigoproctus gig ante us 
(Lucas), contains a minor component that promotes the spread of the 
secretion over the cuticle of arthropod enemies, while at the same time 
accelerating the penetration of the poison (Eisner et al., 1961). The 
following experiments were aimed at determining whether the secre- 
tions of Chlaenius and Abacion are more effective as topical irritants 
to arthropods than pure samples of the phenols they contain. The 
arthropod used for the test was the cockroach Periplaneta americana 
(Linnaeus), and the technique was a slightly improved version of that 
employed previously for comparable purposes (Eisner et al., 1961). 
