Analysis of the chemical composition of the ejaculated repugnatorial secretion of some populations of the Cuban endemic millipede Rhinocricus inhabiting in the western eco-geographical region of the Cuban archipelago has been developed. During research has been identified several quinonoids metabolites (quinones and phenols natural products) as an active components.

Many species of millipedes (Diplopoda) respond to disturbance by coiling up into a tight spiral keeping the head in the centre and ejecting, if further disturbed as defensive strategy, a noxious, topically irritant, with variable composition, fluid, being highly toxic an even cytotoxic.

In the defensive secretions of millipedes have been identified hydrocyanic acid, esters, acids, aldehydes, terpenoids, cyanogenic compounds, phenols, 1,4-benzoquinones, quinazolines, alkaloids, aromatic nitriles, and amino-nitro compounds. The most frequently detected are substituted quinonoids (phenols and 1,4-benzoquinones).

Some individuals (males) gathered from raked forest soil at the edge of the tropical forest, in some cases in typical carst region, were collected and studied. 850 μg of a deep brown-red secretion obtained by means of glass capillary from the individual studied, and directly introduced into analytical instrumental (GC-MS and FTIR)

The analysis of FTIR spectrum and mass spectrum show that the main components of secretions are substituted hydroquinones, substituted 1,4-benzoquinones and aldehydes.

The biological effects of these defensive secretions were evaluated experimentally, on ants (Atta spp.) and on pathogenic microorganisms. The results of the experiments showed a quick repellent effect and very interesting antimicrobial action. The ecological and evolutionary significance of chemical differentiation in millipedes populations are under study.