Life cycle and host specificity of Amblyomma triste (Acari: Ixodidae) under laboratory conditions MARCELO B. LABRUNA 1,4, *, ERIC Y.M. FUGISAKI 1 , ADRIANO PINTER 1 , JOSÉ MAURÍCIO B. DUARTE 2 and MATIAS J.P. SZABÓ 3 1 Departamento de Medicina Veterinária Preventiva e SaúdeAnimal, Faculdade de Medicina Veterinária e Zootecnia, Universidade de São Paulo, São Paulo, 05508-000, SP, Brazil; 2 Departamento de Melho- ramento Genético, Faculdade de Ciências Agrárias e Veterinárias, Universidade Estadual Paulista, Ja- boticabal, SP, Brazil; 3 Departamento de Patologia Veterinária, Faculdade de Ciências Agrárias e Vet- erinárias, Universidade Estadual Paulista, Universidade de Franca, Jaboticabal, Franca, SP, Brazil; 4 Department of Pathology, University of Texas Medical Branch at Galveston (UTMB), Room 4.116 Keiller Building, 301 University Boulevard, Galveston, Texas 77555-0609, USA; *Author for correspon- dence (e-mail: labruna@usp.br; phone: +1-409-772-4813; fax: +1-409-747-2415) Received 25 November 2002; accepted in revised form 17 March 2003 Key words: Amblyomma triste, Host preference, Ixodidae, Life cycle Abstract. We report biological data of two generations of Amblyomma triste in laboratory and com- pared the suitability of different host species. Infestations by larval and nymphal stages were performed on guinea pigs (Cavia porcellus), chickens (Gallus gallus), rats (Rattus norvegicus), rabbits (Oryctola- gus cuniculus), wild mice (Calomys callosus), dogs (Canis familiaris) and capybaras (Hydrochaeris hy- drochaeris). Infestations by adult ticks were performed on dogs, capybaras and rabbits. Tick develop- mental periods were observed in an incubator at 27 °C and RH 90%. Guinea pigs were the most suitable hosts for larvae and nymphs, followed by chickens. The remaining host species were less suitable for immature ticks as fewer engorged ticks were recovered from them. Mean larval feeding periods varied from 3.8 to 4.7 d between different host species. Mean larval premolt periods ranged from 8.9 to 10.4 d. Nymphal mean feeding periods varied from 4.2 to 6.2 d for ticks fed on different host species. Premolt period of male nymphs (mean: 15.4 d) was significantly longer than that of female nymphs (14.7 d). Female nymphs were significantly heavier than male nymphs. The overall sex ratio of the adult ticks emerged from nymphs was 0.9:1 (M:F). Capybaras were the most suitable host for the tick adult stage as significantly more engorged females were recovered from them and these females were significantly heavier than those recovered from dogs or rabbits. The life cycle of A. triste in laboratory could be completed in an average period of 155 d. The potential role of guinea pigs, birds and capybaras, as hosts for A. triste in nature, is discussed. Introduction Amblyomma triste Koch was first described in 1844 from Uruguay but subsequent authors regarded it as synonym of Amblyomma maculatum Kock, described from North America (Kohls 1956). It was until the revision of Kohls (1956), which fi- nally confirmed A. maculatum, A. triste and Amblyomma tigrinum Koch as valid distinct species. Currently, the geographic distribution of A. triste and A. tigrinum is restricted to South America whereas A. maculatum is restricted to southern United © 2003 Kluwer Academic Publishers. Printed in the Netherlands. Experimental and Applied Acarology 30: 305–316, 2003.