MILLIPEDES 29 



human skin. Later the affected part peels, leaving a wound which 

 heals only very slowly. It is dangerous to the eyes and is responsible 

 for numerous cases of blindness among chickens in the West 

 Indies and elsewhere (Burtt, 1947). 



In its smell and colour the secretion of most Opisthospermo- 

 phora resembles iodine and stains the fingers a purplish-brown 

 colour in the same manner as this substance. The chief compounds 

 of physiological interest in the secretions are hydrocyanic acid, 

 iodine and quinine. Small amounts of chlorine which give the 

 substance its characteristic odour have been determined experi- 

 mentally. It has been suggested that the disinfecting properties of 

 the chlorine and hydrocyanic acid may assist in keeping the animal 

 free from bacteria and other micro-organisms. 



In contrast the Proterospermophora rarely secrete visible quan- 

 tities of odoriferous substance, although if a number of Poly- 

 desmid millipedes be gathered together, a distinct almond-like 

 smell becomes discernible. The natives of central Mexico grind up 

 Polydesmus ricinus with various plants to make a poison for their 

 arrows and the large Lysiopetalum foetidissimum takes its name 

 from the obnoxious smell of the secretion from its stink glands. 

 Many of the tropical species exhibit patterns of strongly con- 

 trasted warning colours which are clearly associated with their 

 poisonous nature. The majority of the Colobognatha do not appear 

 to secrete repugnatorial fluids, but species of Polyzonium produce 

 a whitish substance that may have an odour of camphor and is 

 probably again a deterrent to predatory enemies. 



The Oniscomorpha and Limacomorpha curl up into a ball when 

 disturbed and members of the other orders form a more or less 

 compact spiral. These defensive reactions not only render the 

 animals less vulnerable to their enemies, but also are effective in 

 reducing water-loss by evaporation when the millipedes are in dry 

 surroundings. They have been a factor of major evolutionary im- 

 portance (Manton, 1954). 



The minute Pselaphognatha are covered with tufts of peculiar 

 hairs like small pin-cushions which resemble the urticating hairs of 

 some Lepidopterous caterpillars. Like them they are hollow, very 

 easily detached from the body and bear a number of retroverted 

 barbs or processes near their tips and along their axes. These and 



