1982] Eisner & Meinwald — Defensive Spray Mechanism 359 
Aliphotic Acids 
fj.q per Beetle 
Caprylic acid CH 3 (CH 2 ) 6 C0 2 H 25 
Capric acid CH 3 (CH 2 ) 8 C0 2 H 5 
c/s-3-Decenoic acid CH 3 (CH 2 ) 5 CH =CHCH 2 C0 2 H 5 
c/s-4-Decenoic acid CH 3 (CH 2 ) 4 CH =CH(CH 2 ) 2 C0 2 H 5 
Terpene Alcohols 
Lavandulol 
a-Necrodol 
)3-Necrodol 
4 
14 
3 
Fig. 1. Substances isolated and characterized from the rectal gland of Necrodes 
surinamensis. The two terpene alcohols, a-necrodol and 0-necrodol, are new natural 
products; m-3-decenoic acid and m-4-decenoic acid have not previously been 
reported from an insectan source. Details of the chemical procedures will be pub- 
lished elsewhere. 
way of a narrow neck into the rectum. The tubule is surrounded by a 
loose meshwork of muscle fibers, clearly identifiable as such in 
whole mounts of the gland viewed by transmitted polarized light. 
Comparable compressor muscles, arranged in a thick layer, envelop 
the sac. The entire gland has an inner lining of membranous cuticle, 
which was readily isolated by treatment of the gland with 10% 
aqueous potassium hydroxide, and was shown to be continuous with 
the cuticular lining of the hindgut. In freshly dissected preparations, 
both parts of the gland were seen to be filled with clear fluid. The 
hindgut, in contrast, was usually replete with opaque fecal paste. 
The compounds listed in Figure 1 had been shown to be present 
both in extracts of isolated glands and in samples of the spray itself. 
None were present in more than trace amounts in extracts of the 
region of the hindgut anterior to the glandular junction. It seemed 
reasonably certain, therefore, that the fatty acids and terpenes are 
products of the gland rather than the enteron. This conclusion was 
further supported by circumstantial evidence. Fluid squeezings from 
isolated glands, unlike squeezings from the hindgut, gave acidic spot 
