24 BULLETIN OF WISCONSIN NATURAL HISTORY SOCIETY. VOL. 4, NOS. 1-2. 
ISOXITRILES. 
Both sexes of the large Tarantula-hawk (Pepsis spp.) produce 
a distinct isonitrile odor when first captured. This is quite 
noticeable, although often modified by the scent of the honey that 
they have eaten. 
The nasutes of an African species of Ptyotermes eject a 
pungent stream from the head, the nature of which is thus treated 
by Cook ('90) : "The fluid is clear and watery and does not stain 
the hands. A smarting sensation in the eyes and nose is also 
distinctly appreciable. The odor is even more disagreeably 
pungent and penetrating than that of Spirotreptus [a myriapod 
mentioned below] and has an almost nauseating quality which 
pervades the nests and galleries of the species and can readily be 
detected in houses attacked by this termite [isonitriles] . Like the 
secretion of Polyzonium [another myriapod referred to below] the 
liquid becomes sticky on exposure to the air, and the insect 
enemies upon which it is squirted have their antennae stuck to 
their bodies and are othenvise disabled." 
VEGETABLE EXTRACTS, ETC. 
Large numbers of phytophagous insects acquire odors or tastes 
derived from their food plants, but these hardly come in line with 
the present discussion. 
Many of the Darkling beetles, and especially those belonging 
to the genus HI e odes secrete from anal glands a fluid of an in- 
tensely disagreeable odor, which some of the species can forcibly 
eject for a distance of ten centimeters or more. The liquid stains 
the skin brown, besides having a very penetrating odor and thus 
resembles the secretion of Spirobolus (see special part). Accord- 
ing to Williston ('84) it is soluble in water, alcohol and ether, has 
an acid reaction, and can be esterified to an agreeably smelling 
ether by means of alcohol and sulphuric acid. He suggests from 
this the presence of organic acids other than formic or acetic, 
which latter he could not detect. Our commonest species, when 
extracted with ether furnishes an extremely malodorous com- 
pound, suggesting extract of Taraxicum or opium. 
The exuded blood of many Coccinellidse has an opium-like 
odor (Packard 98). The species of the ant genus Cremastogas- 
ter. squirt from their anus a white liquid which recalls the juice 
characteristic of the shelf-fungi. This odor is much more intense 
in another ant, Pachycondla {v. special portion). 
