Hydrogen cyanide from millipede

It is commercially prepared from benzaldehyde and hydrogen cyanide. Mandelonitrile is used by certain insects (tiger beedes, an African millipede) as a defense duid (38). After expelling the duid an enzyme catalyzes the conversion of mandelonitrile to benzaldehyde and HCN, which is usually fatal to the insect s enemy. 

Many plants produce bad-tasting chemicals to protect themselves from plant-eating insects and animals. The familiar compound nicotine deters animals from eating the tobacco plant. The millipede sends an unmistakable back off message by squirting a predator with benzaldehyde and hydrogen cyanide. 

Cyanohydrin chemistry plays a central role in the defense system of Aphelo-ria corrugata. This millipede uses a two-chamber gland much like that used by the bombardier beetle (see A Word About... Quinones and the Bombardier Beetle in Chapter 7) to deliver a secretion that contains hydrogen cyanide. Apheloria stores benzaldehyde cyanohydrin and, when threatened, converts it to a mixture of benzal-dehyde and hydrogen cyanide, which is then secreted. The hydrogen cyanide gas that emanates from the secretion is an effective deterrent of predators. 

The isolation of the glucoside of cuminaldehyde cyanohydrin (XCVI) from the millipede Polydesmus vicinus L. [732] is of great interest since, like the established function of mandelonitrile in Apheloria corrugata [733-735] it could represent a means of delivery of hydrogen cyanide. 

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