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Field Guide to Common Western Grasshoppers: Introduction
by Robert E. Pfadt
List of Species Fact Sheets (60 Species)
Links to "IPM Handbook"
Introduction
Nearly 400 species of grasshoppers are known to inhabit the 17 western states. Of these, approximately 70 species are common enough to be encountered regularly by persons scouting for damaging populations. For personnel who lack taxonomic experience, identifying the nymphs and adults of these common grasshoppers is difficult. Yet the need for considering species in control decisions becomes ever more urgent. Control officials need to know both the identities and the densities of species composing infestations to assess accurately the economic threat and select prudent solutions.
There are several reasons why it is necessary to correctly identify species. (1) Species vary in their biotic potential and in their capacity for causing damage. (2) Depending on their food habits, species may be either pests or beneficials. (3) Certain species of pest grasshoppers are highly migratory and often pose a serious threat to distant crops. (4) Species vary in their seasonal cycle (period of hatching, development, and reproduction), which in turn affects the timing of control treatments. (5) Because current chemical and biological methods of controlling grasshoppers are more sophisticated, their effective use requires greater knowledge of the pests' life histories and habits. (6) As environmental impacts of control are more finely evaluated, recognition of pest species of grasshoppers has become essential in the selection of management strategies.
The purpose of this manual is to provide a pictorial guide that will allow plant protection personnel to make grasshopper identifications in the field. Although the surest method for obtaining an accurate identification is submission of the specimen to a specialist, this procedure is not feasible during an expeditious grasshopper survey. To achieve the requisite efficiency in making a useful survey, the scout must be able to identify, and in a short time learn to recognize on sight, the common species inhabiting the infested area.
Grasshoppers are relatively large insects with quite distinct appearances. Diverse traits permit one to identify a specimen of an unknown species by comparing it with identified museum specimens. One may also identify the specimen by comparing it with good color pictures. When accompanied by illustrations and descriptions of distinguishing characters and their variations, color pictures are probably the best means of accurate identification of an unknown specimen (short of submitting it to a specialist).
This Field Guide to Common Western Grasshoppers provides the scout with color pictures of the nymphs, adult male, and female, and illustrations and descriptions of distinguishing characters allowing comparisons with unknown specimens that need identification. The guide also contains distribution maps of species, brief accounts of their seasonal cycles, feeding and reproductive behavior, and habitat preferences. All may serve as additional clues to the identities of specimens as well as provide pertinent information for grasshopper management.
