Nota Científica

 

Records of predators and parasites (vertebrates and invertebrates) of creosote bush grasshopper Bootettix argentatus Bruner, 1889 (Orthoptera: Acrididae: Gomphocerinae) from the Bolsón de Mapimí, Dgo. (Chihuahuan desert), Mexico

 

Eduardo Rivera García

 

Instituto de Ecología, A. C., Centro Regional Durango. Km. 5 carretera a Mazatlán, esq. Blvd. Los Remedios. Apdo. Postal 632. CP 34000, Durango, Dgo. MÉXICO. riverae@fauna.edu.mx.

 

Abstract

This paper summarizes unpublished information and isolated field observation records on the principal predators (9 vertebrates, 10 insect and 2 orb weaver and a terrestrial spider species) and parasites (an insect and one mite species) of B. argentatus a non economic, highly specialized monophagous grasshopper species of creosote bushes Larrea tridentata in Mapimi Biosphere Reserve, a southern region of the Chihuahuan Desert.

 

The grasshopper Bootettix argentatus, is a monophagous species (Ball 1936, Econ. Ent. 29:679-684; Uvarov 1977. Grasshopper and Locusts. A Handbook of General Acridology. C. O. P. R. London), restricted to living and feeding on creosote bush (Larrea tridentata) (DC) Cov. (Zygophyllaceae), during all its life (Isely 1944, Ann. Ent. Soc. Amer. 37:47-67; Otte & Joern 1977, Proc. Acad. Nat. Sci. Phila. 128:89-126; Joern 1979. Trans. Amer. Ent. Soc. 105:253-300). It occasionally chews on some grasses but does not ingest them (Chapman 1988, In: Chapman, R. F. and A. Joern. Eds. Biology of Grasshoppers. John Wiley & Sons. USA. Pags 39-72). The species is widespread in arid lands in USA, and Mexico, and its distribution closely matching to its host plant (Appendix 1).

The high diet specialization increases the physiological efficiency of this species but can reduce its defensive behaviour against predators and its dispersion capacity (Staddon & Gendron 1983. Amer. Nat. 122:843-848; Moran 1986. Ecology. 67:108-115).

Some years they exhibit densities as high as 30 ind/bush (Thinkham 1948, Amer Midl. Nat. 40:521-663; Otte 1981, The North American Grasshoppers, Vol. 1. Harvard University Press. USA) and population densities ranging from 300 to 700 ind/ha (Mispagel 1978, Ecology. 59:779-788); the grasshopper population can be found around 30% of the creosote bushes observed (N=300, Rivera 1996, Acta Zool. Mex. N. S. 68:1-12), and they can be observed during most of the year, with the highest abundance observed between August and December (Rivera 1986, Acta Zool. Mex. N. S. 14:1-42).

The Hairston et al paper on community structure, population control and competition (1960. Amer. Nat. 94:421-425), demonstrated the importance of food webs. Root and his students (1973, Ecol. Monogr. 43:95-124), further examined some important interactions in insect communities, showing predation as an important control agent on herbivorous insects, affecting the competition between species in the same trophic level and their effect on primary producers. Bernays and Graham, (1988, Ecology. 69:886-892) state that herbivores' natural enemies are a strong selection pressure resulting in a decrease in the host numbers.

From 1930 to 1955, research efforts on insect predators and parasites were focused on biological control of economic pest species. This interest has been renewed in the last decade due to the controversy generated by the use of exotic agents used in Integrated Pest Management Programs. To that end, extensive lists of predators and parasites of economic pest grasshoppers have been generated (Mason & Erlandson 1994, The Can. Ent. 126:1459-1491).

In this paper I present an annotated list of 22 species of predators and 2 species of parasites of the grasshopper Bootettix argentatus in the Mampimi Biosphere Reserve.