On the development of the brown spider Loxosceles gaucho Gertsch (Araneae, Sicariidae): the nympho-imaginal period

Rinaldi, Isabela M.P; Forti, Luiz C; Stropa, André A

doi:10.1590/S0101-81751997000300018

Abstract

Observations of the developmental biology of Loxosceles gaucho Gertsch, 1967, the brown spider of southeastern Brazil are scarce. The present study reports the method of individualized rearing of 18 populations of L. gaucho, kept in laboratory under varied diet conditions, and characterizes their nympho-imaginal period as well as factors related to their reproduction. Females built the first egg sac about 20 days after copulation and nymphs hatched 40 days after the laying date. Average offspring was 61.3 spiderlings and females usually built three to four successive egg sacs in a period of five to seven months. First nymphs initiated their predatory activity between the 5th and 8th days after hatching and the majority reached adulthood within six moults (range of five to eight) in approximately 15 to 17 months (male) and 15.5 to 18 months (female). The average sex ratio equaled 1.0:1.7 (male:female). The wide individual variability of this species intermoult intervals is herewith expressed by the "intermoult rate", which was fairly uniform for both intra and interpopulations and gives a relevant aspect for a general idea of the life cycles of spiders.

Brown spider; Loxosceles gaucho; Sicariidae; development

On the development of the brown spider Loxosceles gaucho Gertsch (Araneae, Sicariidae): the nympho-imaginal period

Isabela M.P. Rinaldi^I; Luiz C. Forti^II; André A. Stropa^I

^IDepartamento de Zoologia, Instituto de Biociências, Universidade Estadual Paulista. Caixa Postal 510, 18618-000 Botucatu, São Paulo, Brasil

^IIDepartamento de Defesa Fitossanitária, Faculdade de Ciências Agranômicas, Universidade Estadual Paulista. Caixa Postal 237, 18603-970 Botucatu, São Paulo, Brasil

ABSTRACT

Observations of the developmental biology of Loxosceles gaucho Gertsch, 1967, the brown spider of southeastern Brazil are scarce. The present study reports the method of individualized rearing of 18 populations of L. gaucho, kept in laboratory under varied diet conditions, and characterizes their nympho-imaginal period as well as factors related to their reproduction. Females built the first egg sac about 20 days after copulation and nymphs hatched 40 days after the laying date. Average offspring was 61.3 spiderlings and females usually built three to four successive egg sacs in a period of five to seven months. First nymphs initiated their predatory activity between the 5^th and 8^th days after hatching and the majority reached adulthood within six moults (range of five to eight) in approximately 15 to 17 months (male) and 15.5 to 18 months (female). The average sex ratio equaled 1.0:1.7 (male:female). The wide individual variability of this species intermoult intervals is herewith expressed by the "intermoult rate", which was fairly uniform for both intra and interpopulations and gives a relevant aspect for a general idea of the life cycles of spiders.

Key words: Brown spider, Loxosceles gaucho, Sicariidae, development.

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ACKNOWLEDGEMENTS. This work was supported in part by Fundação para o Desenvolvimento da UNESP (FUNDUNESP). We are grateful to Mrs. Nedy A. Andrés and Mr. Pedro Evangelista for their care in looking after the spiders in the laboratory and for their help during collections.

Recebido em 17.X.1996; aceito em 10.IX.1997.

Bücherl, W. 1961. Aranhas do gênero Loxosceles e loxoscelismo na América. Ciência e Cultura 13:213-224.
Bücherl, W. & E.E. Buckley. 1971. Venomous animals and their venoms, vol. III. Venomous Invertebrates. New York, Academic Press, XXII+537p.
Foelix, R.F. 1982. Biology of Spiders. Cambridge, Harvard Press, VI+306p.
Galiano, M.E. 1967. Ciclo biológico y desarollo de Loxosceles laeta (Nicolet, 1849). Acta Zool. Lilloana 23:432-464.
Galiano, M.E.& M. Hall. 1973. Datos adicionales sobre el ciclo vital de Loxosceles laeta. Physis 32:277-288.
Gertsch, W.J. 1967. The spider genus Loxosceles in South America (Araneae, Scytodidae). Bull. Amer. Mus. Nat. Hist. 136:117-174.
Horner, N.V. & K.W. Stewart. 1967. Life History of the Brown Spider, Loxosceles reclusa Gertsch and Mulaik. Texas Jour. Sci. 19 (4):333-347.
Levy, G. 1970. The life cycle of Thomisus onustus (Thomisidae: Araneae) and outlines for the classification of the life histories of spiders. Jour. Zool., London, 160:523-536.
Lowrie, D.C. 1987. Effects of diet on the development of Loxosceles laeta (Nicolet) (Araneae:Loxoscelidae). Jour. Arachnol. 15:303-308.
Nentwig, W. 1987. Ecophysiology of spiders. Berlin,Springer-Verlag, IX+488p.
Vachon, M. 1957. Contribuition à l'étude du developpment postembryonnaire des araignées. Premiére note. Généralités et nomenclature des stades. Bull. Soc. Zool. France 82:337-354.
Weems, H.V. & W.H. Whitcomb. 1975. The Brown Recluse spider, Loxosceles reclusa Gertsch and Mulaik (Araneae: Loxoscelidae). Fla. Dept. Agr. & Consumer Serv. 158:1-2.

Publication Dates

Publication in this collection
10 July 2009
Date of issue
Sept 1997

History

Accepted
10 Sept 1997
Received
17 Oct 1996

This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.

[1] Bücherl, W. 1961. Aranhas do gênero Loxosceles e loxoscelismo na América. Ciência e Cultura 13:213-224.

[2] Bücherl, W. & E.E. Buckley. 1971. Venomous animals and their venoms, vol. III. Venomous Invertebrates. New York, Academic Press, XXII+537p.

[3] Foelix, R.F. 1982. Biology of Spiders. Cambridge, Harvard Press, VI+306p.

[4] Galiano, M.E. 1967. Ciclo biológico y desarollo de Loxosceles laeta (Nicolet, 1849). Acta Zool. Lilloana 23:432-464.

[5] Galiano, M.E.& M. Hall. 1973. Datos adicionales sobre el ciclo vital de Loxosceles laeta. Physis 32:277-288.

[6] Gertsch, W.J. 1967. The spider genus Loxosceles in South America (Araneae, Scytodidae). Bull. Amer. Mus. Nat. Hist. 136:117-174.

[7] Horner, N.V. & K.W. Stewart. 1967. Life History of the Brown Spider, Loxosceles reclusa Gertsch and Mulaik. Texas Jour. Sci. 19 (4):333-347.

[8] Levy, G. 1970. The life cycle of Thomisus onustus (Thomisidae: Araneae) and outlines for the classification of the life histories of spiders. Jour. Zool., London, 160:523-536.

[9] Lowrie, D.C. 1987. Effects of diet on the development of Loxosceles laeta (Nicolet) (Araneae:Loxoscelidae). Jour. Arachnol. 15:303-308.

[10] Nentwig, W. 1987. Ecophysiology of spiders. Berlin,Springer-Verlag, IX+488p.

[11] Vachon, M. 1957. Contribuition à l'étude du developpment postembryonnaire des araignées. Premiére note. Généralités et nomenclature des stades. Bull. Soc. Zool. France 82:337-354.

[12] Weems, H.V. & W.H. Whitcomb. 1975. The Brown Recluse spider, Loxosceles reclusa Gertsch and Mulaik (Araneae: Loxoscelidae). Fla. Dept. Agr. & Consumer Serv. 158:1-2.