1982] Eisner & Meinwald — Defensive Spray Mechanism 365 
maxillosus, also mixes intestinal fluid with the secretion of its defen- 
sive glands (Jefson et al., 1983). A diet of carrion, one might imagine, 
could render an insect’s enteric contents potently deterrent. The 
ammonia reportedly present at high concentrations in the anal 
effluent of some silphids (Schildknecht and Weis, 1962) is probably 
derived from decaying ingested animal protein and may well serve 
for defense. To us at least, the odor of the intestinal fluid discharged 
by many carrion insects upon handling, or for that matter the odor 
of the insects themselves, is repugnant. The fragrance emitted by 
Neerodes after a discharge is transient, and certainly does not mask 
the intrinsic stench of the animal. 
While it would have been desirable to test the various secretory 
components of Neerodes for repellency, this proved impossible due 
to lack of sufficient synthetic quantity of a-necrodol and (3- 
necrodol, the two most interesting novel compounds in the mixture. 
It seems likely, however, that these terpenes are deterrent to insects. 
They are cyclopentanoid compounds, of which many are known to 
occur in the defensive glands of insects and in plants (Nakanishi et 
al., 1974), and some are provenly repellent to insects (Eisner, 1964; 
Smolanoff et al., 1975; Meinwald et al., 1977; Jefson et al., 1983). 
Fatty acids have also been reported from other arthropodan defen- 
sive glands. They may themselves be deterrent, and may also serve 
as surfactants. As part of a spray they may promote spread and 
penetration of droplets on target, a role that has been demonstrated 
for caprylic acid in whip scorpion secretion (Eisner et al., 1961). The 
fatty acids of Neerodes may have a similar function, and may also 
facilitate the mixing of the apolar glandular material with the large- 
ly aqueous enteric fluid when the two are discharged together. Two 
of the Neerodes fatty acids, m-3-decenoic acid and ns-4-decenoic 
acid, have not previously been identified from an insectan source. 
The apparent enteric, rather than glandular, origin of stearic and 
palmitic acid should come as no surprise, since these fatty acids are 
major components of animal fats and hence likely to be ingested by 
Neerodes with carrion. 
Only speculation can be offered to account for the presence of 
lavandulol in the Neerodes spray. The substance has not previously 
been reported from insects, although it is known from plants as a 
major component of lavender oil (Karrer, 1958). We suspect the 
compound to be repellent to insects, as some low molecular terpenes 
