THE life cycles of pentastomids, or tongue worms, are little known although the biology of these creatures has been the subject of investigations since the pioneer studies of Rudolf Leuckart1 in 1860. In the adult stage, pentastomids are almost exclusively parasites of reptiles, exceptions being species of Linguatula from carnivores and Reighardia sternae from gulls and terns. The immature stages of these parasites have hitherto been found only in vertebrate animals, ranging from fish to mammals. In every case in which life cycles have been either partially or totally elucidated the intermediate host has always proved to be a vertebrate. As Baer2 says, “It is particularly interesting to record that no larval pentastomid has ever been found in an invertebrate and that, on the other hand, many species of warm-blooded animals can act as intermediate hosts of reptilian parasites”. Our discovery recently of larval pentastomids in cockroaches in Singapore is therefore of unusual significance since it appears to be the first record of the finding of tongue worms in invertebrates.