358 
Psyche 
[Vol. 87 
Procedures and Results 
Necrodes surinamensis is a large beetle, about 2 cm in average 
body length. It occurs throughout the United States, east of the 
Rocky Mountains. It is mostly taken at carcasses. We collected 
large numbers at baits (dead fish and chickens) in the environs of 
Ithaca, New York, and on the grounds of the Archbold Biological 
Station, Lake Placid, Florida. They were maintained in the labora- 
tory on commercial meat-based dog food preparations. Observa- 
tions were made mostly on freshly captured specimens. 
Spray ejection was studied by techniques previously used with 
other chemically protected arthropods (Eisner, 1958). The beetles 
were individually fastened with wax to tethers and placed in normal 
stance upon sheets of indicator paper (filter paper presoaked in red 
alkaline phenolphthalein solution, blotted off to near dryness just 
before use). They were then subjected to simulated attack by pinch- 
ing some of their appendages with forceps or briefly touching parts 
of the body with a hot spatula. Their responses were immediate. No 
sooner had a stimulus been applied than they revolved the abdomi- 
nal tip, which projects free beyond the posterior margin of the ely- 
tra, aimed it toward the site stimulated, and sprayed. As evidenced 
by the pattern of white spots induced by the acid fluid on the indica- 
tor paper, the discharges were accurately directed (Fig. 2A, B). The 
site of emission of the spray was clearly noted to be the anus. The 
abdominal tip is essentially a revolvable emplacement for the anal 
nozzle. It can be pointed in all directions, even anteriorly over the 
beetle’s own back (Fig. 2C-F). Regions of the body stimulated were 
always noticeably wetted by the spray. Beetles that had remained 
undisturbed in confinement for several days, and were tethered 
without being caused to discharge (they were kept refrigerated dur- 
ing the tethering procedure), proved capable of spraying repeatedly, 
even in quick succession if a rapid sequence of stimuli was applied. 
The number of discharges (x ± sd) that could be elicited from such 
beetles was 4.9 ± 1 . 1 (N = 5 females + 3 males). Only direct contact 
elicited discharges. The beetles never sprayed in response to move- 
ment or tapping nearby. 
The rectal gland, which is identical in both sexes, was readily 
exposed by dissection. It consists of a tubule and a sac (Fig. 3). The 
tubule lies free in the hemocoel, is long and narrow (actual meas- 
urement in a female = 18 X 0.2 mm) and closed at its distal end. It 
opens proximally into the bladder-like sac, which itself opens by 
