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1 September 2011 Management and Conservation Dilemmas Surrounding a Near-Threatened Grasshopper, Aularches miliaris Linn. (Orthoptera: Pyrgomorphidae) in South India
A. Josephrajkumar, P. Rajan, R. Chandra Mohanan, P.M. Jacob
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Abstract

The world is facing severe biodiversity loss and agencies worldwide are attempting to stem this threat. However problems arise when a rare or threatened species is also an agricultural or medical pest. In this paper we discuss the case of Aularches miliaris, the spotted coffee grasshopper. This species exists as several subspecies across south Asia, perhaps representing local genetic adaptation. It is polyphagous and a minor agricultural pest, and is usually managed via insecticides and egg-bed destruction. For much of its range, populations appear healthy and are not threatened. In contrast, within the Western Ghats Biodiversity Hotspot in south India, A. miliaris is sparse and listed as Near-Threatened. In this area the insect is an occasional minor agricultural pest. Considering its local rarity, versus its abundance in other geographic areas, we recommend that in south India A. miliaris needs to be conserved at the present time. During localized outbreaks, we recommend that A. miliaris be managed via mechanical collection of nymphs and adults, and destruction of egg pods, rather than intervention using insecticides.

The world is currently facing massive biodiversity loss due to human overpopulation, habitat destruction and fragmentation, climate change, the effects of invasive species, disease, pollution, excessive recreational use and harvesting, and natural ongoing geological processes (Wagner & Van Driesche 2010). Mawdsley & Stork (1995) estimate that 11,200 insect species may have gone extinct since the 1600s, and that butterfly species are disproportionally affected. The 2008 World Conservation Union's “Red List of Threatened Species” lists 17,000 threatened species of which more than 600 are insects and 68 are Orthoptera.

Considerable efforts are being made to avert further biodiversity loss. Among these are actions which include captive breeding, establishing seed and gene banks, bans on fishing and harvesting, creation and management of parks, preserves, sanctuaries, and conservation areas, and regulatory enforcement (Williams & Hoffman 2009). However, while we are attempting to preserve some species, we are attempting to eradicate others. Excessive human population growth requires ever-increasing agricultural production in the face of declining farmland, fisheries, water, energy, and fertilizer availability. As such, it is evermore imperative to reduce or eradicate populations of agricultural pests.

But, herein lies a conundrum: what do we do when a population is both a pest and endangered? In such cases there is a conflict between reducing and increasing population numbers (Samways & Lockwood 1998). Hence, conservation of rare and threatened species can be quite complex. An example of conflicting management strategies is seen when a species is rare in one geographic area, but common or pestiferous in another geographic area. The katydid Decticus verrucivorus (L.) is threatened in Britain, yet common in parts of continental Europe (Samways & Harz 1982), and the cricket Gryllotalpa gryllotalpa L. is listed as endangered in Britain (Haes 1987), yet is a well-known pest elsewhere within its natural range in Europe, Asia and North America (Hill 1987).

Pest management also conflicts with conservation when blanket application of pesticides harms hundreds of other nontarget species (Ware 1980). Examples include area-wide spraying for mosquitoes, fire ants, and locusts (Peveling et al. 1994, Lockwood 1998).

A great many species that can harm humans are threatened or endangered. Examples include tigers, lions, panthers, wolves, bears, and sharks that sometimes kill humans or livestock (Quammen 2003). Elephants and some threatened primates sometimes invade the gardens of subsistence farmers (Jayant et al. 2007). In the western USA, poisonous snakes are often killed on sight, and some communities encourage “rattlesnake roundups”, whereby people catch and kill as many snakes as they can find in a day (Hayes et al. 2008). Despite their potential to harm humans, many of these “harmful” species are charismatic, play essential roles in the community, are biologically unique and fascinating and therefore deserve preservation (Quammen 2003).

Other species can be harmful at high density but beneficial at low density. For example, high density populations of Melanoplus sanguinipes (F.) can devastate rangeland and cropland, but at low densities this species may be beneficial, preferring to feed on low-value forbs or noxious weeds (Pfadt 1994). This pattern of feeding on low-value plants at low densities and high-value plants at high densities appears common in Melanoplus, so that labeling these grasshoppers as pests (Vickery 1994) is a simple but an inaccurate approach to grassland management.

The ∼24,000 described species of Orthoptera (Orthoptera Species File) span the range of harmful to beneficial, abundant to rare. Many endangered Orthoptera species are confined to a small geographical area and are highly threatened by anthropogenic impacts that coincide with their restricted ranges. Some formerly widespread and abundant species have become extinct in the recent past (Lockwood & DeBrey 1990, Samways & Lockwood 1998). Other orthopterans can reach very high numbers without becoming pests because their feeding does not threaten, and may even benefit, humans. For example, although potentially devastating to crops, high densities of the Mormon cricket, Anabrus simplex Haldeman, rarely if ever cause significant damage to rangeland (Redak et al. 1992). So also is the case of the snakeweed grasshopper, Hesperotettix viridis (Scudder), which can reach densities of 30 m-2, but feeds exclusively on poisonous plants (Pfadt 1994).

The above examples serve to illustrate that management of pest populations frequently conflicts with conservation. We report here on an interesting grasshopper, the spotted coffee grasshopper, which is both Near-Threatened (NT) in south India, and an agricultural pest. We first provide background on the bionomics of this insect, and then present some management recommendations for populations in Kerala, south India

Fig. 1.

a) Egg pod of Aularches miliaris broken open to show cigar-shaped eggs. b) Nymphs of A. miliaris aggregating on Clerodendron sp. leaf in Kerala, India. c) Adult male showing aposematic coloration. d) Adult A. miliaris ejecting bitter defensive secretion from thorax in response to handling. For color version, see Plate VII.

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Bionomics and life-history of the spotted coffee grasshopper.Aularches miliaris Linn. (Orthoptera: Pyrgomorphidae) is a south Asian species, distributed across much of India, Bangladesh, Cambodia,