whether they actually mate in nature without first feeding. Another Aponomma species, A. concolor, which was examined for its ability to produce elongated spermatids without an adult blood meal, yielded similar results to those obtained from A. hydrosauri. Twoand 3-day-old, unfed males contained testes one-third to one-fourth full of rounded and elongating spermatids, whereas testes of 5to 6-day-old males were full of elongated spermatids. Although the critical experiment has not been conducted to demonstrate whether unfed, male A. hydrosauri and A. concolor will transfer spermatids to females, it is clear that fully mature spermatids are present. Interestingly, recent, unpublished information indicates that another Australian Metastriata tick, Amblyomma triguttatum, shows maturation similar to Aponomma hydrosauri and Aponomma concolor. Unfed male Amblyomma triguttatum can copulate and transfer spermatophores filled with elongated spermatids to females (Guglielmone and Moorhouse, pers. comm.). Species of Aponomma are often considered to be primitive (or specialized) Amblyomma, thus, phylogenetically A. triguttatum is rather closely related to the two Aponomma species. Obviously it is not as closely related to these two as it is to other congeneric species that require feeding before they produce spermatids. These three species with autogenous spermatid maturation also share another similarlity, viz., all have hether they actually mate in nature without irst feeding. nother Apon mma species, A. concolor, hich was examined for its ability to produce longated spermatids without an adult blood eal, yielde similar results to hose obtained rom A. hydrosauri. Twoand 3-day-old, unfed lower chromosome numbers than most of their congeneric relatives (Oliver, 1977, Ann. Rev. Ent mol. 22: 407-429). Aponomma hydrosauri infests a number of large reptile hosts, including skinks (Tiliqua and Trachydosaurus species), dragons (Amphibolurus) and goannas (Varanus species), and the echidna (Tachyglossus species). However, the most commonly recorded host is the sleepy lizard, Trachydosaurus rugosus (Smyth, 1973, Aust. J. Zool. 21: 91-101). Aponomma concolor appears confined to the echidna, Tachyglossus aculeatus and T. setosus. Amblyomma triguttatum feeds on a wider host range of species including marsupials, livestock and other domesticated animals (Roberts, 1970. Australian ticks. CSIRO, Australia, Melbourne, 267 p.). The discovery of species of Metastriata that are able to produce elongated spermatids without a blood meal represents the first exception in this taxon to the general rule of a need for adult feeding before spermatid production and mating occurs. This finding has important implications to studies dealing with reproduction, nutrition, hormones, phylogenetics, population density and vector-pathogen relationships of ticks. This work was supported in part by Grant 09556 from the National Institute of Allergy and Infectious Diseases (NIH), U.S.A., and the CSIRO Long Pocket Laboratories, Indooroopilly, Queensland, Australia.