Modified from the Second Edition, Wyoming Agricultural Experiment Station Bulletin 912, September 1994 for electronic publication
by Spencer Schell and Scott Schell
For some time, supervisors and grasshopper scouts have desired a practical means of identifying common species of grasshoppers in both nymphal and adult stages. The consensus of ideas of APHIS and ARS personnel focused on a field guide that would picture in color not only the adults but also all nymphal instars. In addition the guide should include pictures of diagnostic features of each species. Treatment of 50 species was originally contemplated, but the number increased to 70 as more consideration was given to the species of grasshoppers frequently encountered by scouts working in the 17 western states. Names of 70 species (mainly Acrididae, a few Tettigoniidae) were selected by the technical committee of the Grasshopper Integrated Pest Management Project (QUSDA 1987-94) and are listed in the project outline of the field guide. From this list the author chose six to twelve species to work on annually. Selection was made on the basis of availability of grasshopper species and of site proximity.
Because new employees often need instruction on grasshopper structure, life history, behavior, and ecology, an introduction covering these subjects was also proposed. The project originally was estimated to be completed in two years but it was soon realized that more time was needed. The first species chosen were common, abundant ones inhabiting sites close to Laramie. As fact sheets on these species were completed, sites farther from Laramie chosen for other common grasshoppers entailed more travel time and left less time for productive work. The paucity of published information on the less researched species and less unpublished data in files of the author required first-hand laboratory and field observations. Another problem encountered was the low densities of certain otherwise common species over the last five years, making observation and collection of live specimens more difficult. In spite of these impediments the publication of two new fact sheets in 1994 brings the total number of species treated to 39. We are gathering data and photographing additional species in the summer of 1994. Completion of fact sheets on these will bring the total number to 50.
The need for additional copies of the Field Guide to Common Western Grasshoppers for inclusion in the User Handbook of the Grasshopper Integrated Management Project has provided the opportunity to revise and to add new subjects to the introductory bulletin. These subjects include the following:
The production of this Field Guide to Common Western Grasshoppers has required the
efforts and expertise of several staff members of the University of Wyoming. I wish
to acknowledge their valued contributions that made this publication possible and
the contributions of the professionals of Frontier Printing, Cheyenne, Wyoming.
Allory Deiss, graphic artist
Elizabeth A. Donahue, graphic artist
Dana Lynn Dreinhofer, publications editor
Kim Gould, publications editor
Kirsten Keeton, graphic artist
Herbert D. Pownall, photographer
Elizabeth Ono Rahel, graphic artist
Karen D. Singer, typist
Carol L. Stevens, graphic artist
William L. Stump, artist
Ellyn Sturgeon, word processor
I gratefully acknowledge the assistance of Shanna Breeding, Mark Carter, Donald Hostetter,
Boris Kondratieff, John Larsen, Tim McNary, Bill Elliott, Bruce Shambaugh, Robert
Stuckey, and David Weissman in locating species of grasshoppers and providing specimens,
and the help of Burrell E. Nelson of the Rocky Mountain Herbarium in identifying plants.
I also wish to acknowledge the peer review of the manuscript by my colleagues Jeffrey
C. Burne, E.W. Evans, Robert J. Lavigne, Jeffrey A. Lockwood, and Bruce Shambaugh.
Funding for the publication of the Field Guide to Common Western Grasshoppers was
provided through a grant to the University of Wyoming from the U.S. Department of
Agriculture's Animal and Plant Health Inspection Service (APHIS)/Grasshopper Integrated
Pest Management Project. The university and author gratefully acknowledge the support
of APHIS, which made this publication possible.
College of Agriculture • The University of Wyoming
Steve W. Horn, Director, Agricultural Experiment Station, University of Wyoming, Laramie
82071.
Persons seeking admission, employment or access to programs of the University of Wyoming shall be considered without regard to race, color, national origin, sex, age, religion, political belief, disability, veteran status and marital or familial status. Persons with disabilities who require alternative means for communication or program information (braille, large print, audiotape, etc.) should contact their local UW Extension Office. To file a complaint, write the UW Employment Practices/Affirmative Action Office, University of Wyoming, P.O. Box 3354, Laramie, Wyoming 82071-3354.
Information given here is supplied with the understanding that no discrimination is intended and no endorsement by the University of Wyoming Agricultural Experiment Station is implied on trade or brand name commodities.
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.
The basis for classification and identification of grasshoppers consists primarily of the distinctive features of their external anatomy. Gross structures establish the affiliation of grasshoppers with the higher categories of invertebrate animals. For example, grasshoppers belong to the phylum Arthropoda as evidenced by the ringlike segments of their body, their jointed appendages, and their exoskeleton (Fig. 1).
Figure 1. Diagram of a female grasshopper showing characteristic external features. Modeled after Melanoplus bivittatus (Say).
Further segregation places them in the class Insecta, the insects. They have three
body regions (the head, thorax, and abdomen) and possess a tracheal system for breathing,
three pairs of legs, and two pairs of wings. Within the Insecta, grasshoppers belong
to the order Orthoptera, as they grow and develop by gradual metamorphosis (eggs-nymphs-adults),
and they have chewing mouthparts and leathery forewings called tegmina. Grasshoppers
may next be placed in the family Acrididae because they possess short antennae and
ovipositor (egg-layer), an auditory organ (tympanum visible externally) on each side
of the first abdominal segment, and three-segmented tarsi (feet). See Table 1 summarizing
the affiliation of the Carolina grasshopper, Dissosteira carolina (Linnaeus).
For placing grasshoppers in lower categories of classification, that is, in genus and species, one must resort to finer structures of their external anatomy and also to body size, shape, color, stripes, and patterns. Anatomical structures often have special names that the scout must learn in order to understand the descriptions of species in this guide.
Identification of grasshopper nymphs presents greater difficulties because of the absence of several reliable taxonomic characters of the adult stage. In nymphs, the wings are lacking and the genitalia are undeveloped and generalized. Sets of characters, however, are useful in identifying nymphs of the three large subfamilies of western grasshoppers. The chief characters diagnostic of slantfaced nymphs (Gomphocerinae) consist of the degree of facial slope, general color pattern, shape of the antennae and foveolae, and the extent of curving of the lateral carinae of the pronotum. Chief characters diagnostic of bandwinged nymphs (Oedipodinae) are: (1) height of the median carina of the pronotum and number of sulci; (2) position and length of the lateral carinae; (3) color patterns of the hindlegs; (4) variations in dark bands on the head and pronotum; and (5) shape of the foveolae. Chief characters diagnostic of spurthroated nymphs (Melanoplinae) are color patterns of the hind femur, color patterns of the gena and pronotum,and markings of the compound eyes. The characters of the compound eyes, namely, color, stripes, and number and size of spots, are evident in fresh specimens, but they disappear in specimens that have been held for any length of time, even frozen ones. In treatment of the individual species later on, the particular diagnostic characters of each are described and explained.
Grasshoppers have been collected, studied, and named from all but the most frigid regions of the earth. More than 10,000 species have been classified and given scientific names. These are binomials, a method of naming used by the Swedish biologist, Carolus Linnaeus (1707-78) in his book, Systema Naturae. The method proved so successful that other biologists promptly adopted it. The tenth edition of Systema Naturae (1758) has been designated as the official beginning for zoological nomenclature. This classic book contains an account of the widely distributed North American grasshopper, Dissosteira carolina (Linnaeus).
In addition to the scientific name, species of grasshoppers may have good common names. Some are approved by the Entomological Society of America, such as the Carolina grasshopper for D. carolina. Nevertheless, in searching the literature and in communicating information on species of grasshoppers, the scientific name has an unrivaled advantage. All of the known species have scientific names while only a small fraction have generally accepted common names.
The scientific name of a species consists of two parts. The first is the name of the genus, a taxonomic category containing a group of closely related species. The second part is the specific epithet or species name. For example, Dissosteira is the name of the grasshopper genus that contains four species; carolina is the specific epithet of one of the four species. The two words together, Dissosteira carolina, comprise the scientific name of the Carolina grasshopper. After the two words the name of the describer, Linnaeus, provides extra information. Linnaeus' name is in parenthesis, which means that originally Linnaeus had placed this species in a different genus ( Gryllus) and another taxonomist later revised the scientific name by placing the species in a new or different genus. A describer who has assigned a newly described species to an established genus is not named in parentheses, for example Melanoplus confusus Scudder.
The scientific name is always italicized. After it has been written in full once, it is usually abbreviated by using the initial of the genus, followed by the full spelling of the epithet, and the dropping of the describer's name, hence D. carolina. The first letter of the genus name is always capitalized and the first letter of the specific epithet is always lower case. The genus name may be used alone when referring to the genus only or to all of the species making up the genus such as Dissosteira or Melanoplus.
How do taxonomists choose a scientific name for a species new to science? Rules of Latin grammar must be followed but otherwise there is much latitude in selecting a name. If the new species can be assigned to a valid genus, a specific epithet not already in use within the genus is chosen. The name may describe a character of the grasshopper or locate the region or state where it was collected. Or it may honor a friend or a renowned scientist. For example, in a taxonomic study published in 1897, Samuel Scudder named a new species Melanoplus bruneri in honor of professor Lawrence Bruner, a pioneer grasshopper specialist at the University of Nebraska, Lincoln. To be a valid scientific name, the author must publish the description and name of a new species in a journal article, bulletin, or book.
As a finishing touch in establishing the authenticity of a new species, the describer chooses a particular specimen as the type or holotype. In the taxonomy of grasshoppers, the type selected by the author is an adult male from which the original description and illustrations were made. A female specimen is also chosen for description and illustration and is specified as the allotype. The author uses other specimens, termed material, for comparison with the types, often describing slight differences in size and color. These may be designated as paratypes, both males and females.
The taxonomist must also decide on the deposition of the types in an insect museum. If the author is a member of the staff of a particular museum, the types are usually deposited with that museum. In cases where the author is not employed by a museum, the types are sent to a recognized museum. Many grasshopper types are held in the extensive collections of the Academy of Natural Sciences of Philadelphia, the California Academy of Sciences (San Francisco), the Museum of Zoology, University of Michigan (Ann Arbor), the Lyman Entomological Museum (Ste. Anne de Bellevue, Quebec), and the National Museum of Natural History (Washington, DC). These are favored museums for the deposition of grasshopper types. The author may send the types to one museum and paratypes to the others and, if there is sufficient material, still other specimens to smaller museums.
Although the grasshopper fauna of North America is relatively well known, new species continue to be found in all parts of the continent and to be described in entomological publications. The chance is slim, however, that a scout will pick up a new species where grasshopper infestations occur. In most instances the scout will be able to identify a specimen from the pages of this field guide. On occasion a scout may collect an already described species not treated in the guide, particularly in genera with large numbers of species such as Melanoplus and Trimerotropis. The scout may then resort to a state grasshopper "key" (see Selected References).
What are species? Species in Latin merely means "kind" and so species in an elementary sense are different kinds of organisms. Most, if not all, species of grasshoppers can be distinguished on the basis of obvious anatomical and behavioral characters and are biological realities. In nature, species consist of populations of individuals that usually occur over an extensive geographic range. For this reason one modern view considers a species to be a genetically distinctive group of natural populations that share a common gene pool and are reproductively isolated from all other such groups. The species is the largest unit of population within which effective gene flow occurs or can occur. Higher taxonomic categories, from the genus up, are biologists' inventions that exist only in the human mind. Animals in the same category have anatomical similarities showing clear relationships. Their grouping, however, is a decision based on a mix of objective and subjective evaluations. One taxonomist's family can easily be another's order.
Grasshopper infestations or assemblages consist of the individuals of several species that live together in the same habitat sharing or competing for available food and space. Members of the dominant species outnumber members of other species and may make up more than 50 percent of the assemblage. Occasionally two or three species may become codominants. No evidence has been found for any essential relationship among species that brings them together. The habitat affords the minimum requirements for all the permanent species and ample measure for the abundant.
Grass-feeding species of grasshoppers are the most numerous in grasslands. In a northern mixedgrass prairie site 18 miles northwest of Fort Collins, Colorado, a total of 24 species were recorded during an outbreak in 1981 (Table 2). Of the total, 14 were grass feeders, six were mixed feeders, and four were forb feeders. The number of individuals of grass-feeding species made up 85% of the total population. The dominant grasshopper, Ageneotettix deorum (Scudder), contributed 52% of the population. A second example of an outbreak population in northern mixedgrass prairie was the assemblage inhabiting a site 15 miles north of Hartville, Wyoming, where 16 species were recorded (Table 2). Nine species were grass feeders, one a mixed feeder, and six were forb feeders. The number of individuals of grass feeding species made up 89% of the population. The dominant grasshopper, Aulocara elliotti (Thomas), contributed 74% of the population.
| NUMBER/SQ YD | |||
|---|---|---|---|
| Mixedgrass Colorado |
Mixedgrass Wyoming |
Desert grass Arizona |
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| Gomphocerinae | |||
| Aeropedellus clavatus |
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- |
| Ageneotettix deorum |
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| Amphitornus coloradus |
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| Aulocara elliotti |
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| Aulocara femoratum |
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- | - |
| Boopedon nubilum | - | - |
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| Cordillacris crenulata | - |
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- |
| Cordillacris occipitalis |
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- | - |
| Eritettix simplex | + | - |
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| Opeia obscura |
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- | - |
| Phlibostroma quadrimaculatum |
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- | - |
| Psoloessa delicatula |
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| Oedipodinae | |||
| Arphia pseudonietana |
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- | - |
| Camnula pellucida | - |
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- |
| Hadrotettix trifasciatus | - |
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| Mestobregma plattei | - | - |
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| Metator pardalinus |
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| Spharagemon equale |
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- | - |
| Trachyrhachys kiowa |
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- | - |
| Trimerotropis pallidipennis | - | - |
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| Xanthippus corallipes |
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| Melanoplinae | |||
| Hesperotettix viridis |
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- |
| Melanoplus bivittatus |
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- | - |
| Melanoplus confusus |
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- |
| Melanoplus cuneatus | - | - |
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| Melanoplus foedus |
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- |
| Melanoplus gladstoni |
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- | - |
| Melanoplus infantilis |
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- |
| Melanoplus keeleri |
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- | - |
| Melanoplus occidentalis |
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- |
| Melanoplus sanguinipes |
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| Total grasshoppers /sq yd |
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| Number species |
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| + indicates species present but not recorded in sampling |
Why was A. deorum dominant in one mixedgrass prairie site and A. elliotti dominant in another? And why was Cordillacris occipitalis (Thomas) the second most abundant in one site and entirely missing from the other? Answers to these questions are not available. An hypothesis for the cause of the observed variations in densities was the differences in habitat in conjunction with differences in requirements of the grasshoppers. Although both sites are part of the northern mixedgrass prairie, the soil, slope, and vegetation of each differ significantly. Grasshopper species vary in densities and dominance depending on the soil, vegetation, topography, and use of a habitat. Because of differential effects of weather, parasites, disease, or insecticidal treatments, the densities of grasshopper species inhabiting a rangeland site may change with time. The abundant species, however, tend to retain their dominant status over the years.
| Tallgrass prairie | Bunchgrass prairie | Sand prairie |
|---|---|---|
| Ageneotettix deorum Melanoplus bivittatus Melanoplus differentialis Melanoplus femurrubrum Orphulella speciosa Phoetaliotes nebrascensis Syrbula admirabilis |
Aulocara elliotti Conozoa sulcifrons Cordillacris occipitalis Dissosteira spurcata Melanoplus sanguinipes Oedaleonotus enigma Trimerotropis pallidipennis |
Ageneotettix deorum Melanoplus angustipennis Melanoplus flavidus Melanoplus foedus Mermiria bivittata Opeia obscura Phoetaliotes nebrascensis |
| Northern mixedgrass prairie | Shortgrass prairie | Annual grassland |
| Aeropedellus clavatus Ageneotettix deorum Amphitornus coloradus Aulocara elliotti Aulocara femoratum Camnula pellucida Cordillacris occipitalis Encoptolophus costalis Melanoplus infantilis Melanoplus sanguinipes Opeia obscura Phlibostroma quadrimaculatum Psoloessa delicatula |
Cordillacris crenulata Hadrotettix trifasciatus Melanoplus gladstoni Opeia obscura Trachyrhachys aspera Trachyrhachys kiowa |
Camnula pellucida Dissosteira pictipennis Dissosteira spurcata Melanoplus devastator Melanoplus marginatus Melanoplus sanguinipes Oedaleonotus enigma |
| Southern mixedgrass prairie | Desert prairie | Cold desert shrub |
| Ageneotettix deorum Amphitornus coloradus Aulocara elliotti Boopedon nubilum Melanoplus sanguinipes Mermiria bivittata Opeia obscura Orphulella speciosa Phlibostroma quadrimaculatum |
Ageneotettix deorum Amphitornus coloradus Aulocara elliotti Hadrotettix trifasciatus Melanoplus cuneatus Melanoplus sanguinipes Trimerotropis pallidipennis |
Aulocara elliotti Cordillacris occipitalis Dissosteira spurcata Melanoplus rugglesi Oedaleonotus enigma Trimerotropis pallidipennis |
| Mountain meadows | Disturbed land (reversions, roadsides, crop borders) |
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| Aeropedellus clavatus Anabrus simplex Camnula pellucida Chorthippus curtipennis Melanoplus alpinus Melanoplus borealis Melanoplus bruneri Melanoplus dawsoni Melanoplus sanguinipes Stenobothrus brunneus |
Aeoloplidesturnbulli Dissosteira carolina Melanoplus angustipennis Melanoplus bivittatus Melanoplus differentialis Melanoplus femurrubrum Melanoplus lakinus Melanoplus packardii Melanoplus sanguinipes |
The composition of grasshopper assemblages is characteristic of various grassland types. A scout working in a western state expects particular species to compose economic infestations in certain areas. Table 3 lists species abundant in several grassland types and in disturbed land (crop borders, fence rows, reversions, roadsides). Because the species composition of grasshopper assemblages infesting particular habitats remains almost the same year after year, a scout is aided in identifying nymphs by knowing the species that were present as adults during past years. Widespread species with high biotic potential, such as Aulocara elliotti and Ageneotettix deorum, inhabit many grassland types and become abundant members in various assemblages of grasshoppers. In outbreaks on desert grasslands of Arizona and New Mexico, for example, A. elliotti is often the dominant species (Table 2), as in many infestations of the northern mixedgrass prairie.
There are probably as many grasshopper life histories as there are grasshopper species. Each species appears to possess a unique set of ecological and physiological adaptations that allow it to grow, survive, and reproduce in its environment. The habitat furnishes individuals with nutritive food plants, adequate living space, satisfactory soil conditions for the eggs, and favorable or tolerable physical and biotic relationships for all the life stages. Because of the distinctive habits and behaviors of grasshoppers, the particular facts of their life histories will be discussed later in treatment of the individual species.
An important component of grasshopper life history is the seasonal cycle - the timing of the periods of egg hatch, nymphal growth and development, emergence of the adults and acquisition of functional wings (fledging), and the deposition of eggs or reproduction. The occurrence of these periods varies among the species and is greatly influenced by weather. An early spring hastens these events and a late one delays them. Latitude also influences the dates of occurrence. In North America springtime comes earlier in the south and later in the north. Consequently, hatching, development and maturation come earlier in the south and later in the north. In the West, altitude is also an important factor. The lower temperatures of higher altitudes, especially those of mountain meadows, are responsible for retarded seasonal cycles of grasshoppers and may often cause a two-year life cycle among species that ordinarily have a one-year life cycle.
Nymphal and adult grasshoppers are present all year long in natural habitats. Several species overwinter in late nymphal stadia and become adult in early spring. The majority, however, pass the winter as eggs protected in the soil. Depending on the species, these eggs hatch at different times from early spring until late summer. The variety of seasonal cycles allows actively feeding and developing grasshoppers to spread out over the entire growing season. Each species has its own time to hatch, develop, and reproduce, but with much overlapping of the cycles. An experienced scout going into the field to survey expects to find certain species at certain times and is thus aided in making identifications. Table 5 arranges the seasonal cycles of grasshoppers into: (1) very early nymphal and adult group, (2) very early hatching group, (3) early hatching group, (4) intermediate hatching group, and (5) late hatching group. The table is especially helpful in the identification of young nymphs.
| Slantfaced | Bandwinged | Spurthroated |
|---|---|---|
| (Gomphocerinae) | (Oedipodinae) | (Melanoplinae) |
| Early spring, large nymphs and adults. Overwintered in nymphal stage. | ||
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| Very early hatching group, hatching in early spring. | ||
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| Early hatching group, hatching in mid-spring. | ||
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| Intermediate hatching group, hatching in late spring. | ||
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| Late hatching group, hatching begins in early summer. | ||
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A grasshopper's day (and night) are linked closely with the physical factors of the environment, especially temperature, but also light, rain, wind, and soil. Stereotyped and instinctive behavior patterns serve grasshoppers remarkably well in making adjustments to wide fluctuations of physical factors that otherwise might be fatal. Grasshoppers effectively exploit the resources of their habitat and at the same time are able to tolerate or evade the extremes of physical factors. Their characteristic rapid jumping and flying responses help them escape numerous enemies that parasitize or feed upon them.
In temperate North America, certain behavior patterns are held in common among grasshopper species, especially among those occupying the same part of the habitat, while other patterns differ. Individuals of different species have different ways of spending the cool nights. Some retreat under litter or canopies of grasses; others squat on bare ground and take no special shelter. Still others may climb a small shrub or a tall grass plant and rest at various heights within the canopy. Under favorable conditions of temperature and other elements of weather, grasshoppers may be active and even feed during the night. In southwestern states they have been observed on warm nights wandering about on the ground and on vegetation, feeding, and stridulating. Several species have been recorded flying at night and are attracted to city lights. A temperature of 80½F is apparently a prerequisite for night flying with maximum flight activity occurring at temperatures above 90½F.
A grasshopper's day usually starts shortly after dawn. Because body temperatures have fallen during the night, a grasshopper on the ground crawls to an open spot, often on the east side of vegetation, that allows it to warm itself by basking in the radiant rays of the sun. A common orientation is to turn a side perpendicular to the rays and lower the associated hindleg, which exposes the abdomen. Those that have spent the night on a plant make adjustments in their positions to take advantage of the sun's rays or they may climb or jump down to the ground to bask. Although grasshoppers generally remain quiet while they bask, they occasionally stir, preen, turn around to expose the opposite side, and sometimes crawl to a more favorable basking location. Grasshoppers may bask for a second time in the cool of late afternoon. Then as shadows begin to engulf the habitat, they retreat into their customary shelters.
After basking for one to two hours on sunny days, grasshoppers become active. They may walk about, seek mates, or feed. Because grasshoppers are cold-blooded creatures, their usual daily activities are interrupted when the weather turns cold, overcast, or rainy. During such times they generally remain sheltered and inactive.
During warm sunny weather of late spring and summer, grasshoppers take advantage of two foraging periods, one in the morning and one in the afternoon. Different species of grasshoppers have different ways of attacking and feeding on their host plants. Individuals of certain species climb the host plant to feed on leaves, petals, buds, or soft seeds while others cut and fell a grass leaf and feed on it while sitting on the ground. Geophilous (ground-dwelling) species regularly search the ground for food, picking up and feeding on seeds, dead arthropods, and leaves felled by other grasshoppers. In grasslands with considerable bare ground, very little litter is produced by grasshoppers. Severed leaves, dropped by the grasshoppers that feed on the host plant, are soon found and devoured by the ground foragers. In habitats infested by dense populations of grasshoppers, pellets of their excrement, rather than litter, accumulate in small conspicuous piles. Only in habitats of tall grass do grasshoppers produce leafy ground litter that goes uneaten and "wasted." This is because the grasshopper species in these habitats are phytophilous and feed resting on the host plant.
Grasshoppers fastidiously select their food. By lowering their antennae to the leaf surface and drumming (tapping) it with their maxillary and labial palps, grasshoppers taste a potential food plant. Gustatory sensilla located on the tips of these organs are stimulated by attractant and repellent properties of plant chemicals, allowing a grasshopper to choose a favorable host plant and reject an unfavorable one. A grasshopper may take an additional taste by biting into the leaf before it begins to feed freely. Phagostimulants are usually important ones nutritionally -certain sugars, phospholipids, amino acids, and vitamins. Grasshoppers may even make choices among the leaves of a single host plant. They prefer young green leaves and discriminate against old yellowing ones. Nevertheless, individuals of ground-dwelling species often feed in short bouts on old plant litter lying on the ground as well as on dry animal dung. This feeding may be a means of restoring water balance - either losing or gaining moisture.
Later, in the species fact sheets, grasshopper food plants are referred to by their common names. The appendix beginning on page 29 provides a listing of these with their scientific names to clarify any ambiguities.
Amazingly, grasshoppers are able to communicate visually and acoustically among themselves. They produce sounds with structural adaptations on hindlegs and wings and receive these signals with auditory organs (ears) located in the first abdominal segment (Fig. 8). Using their colorful wings and hindlegs they also flash visual messages and receive these with their compound eyes. Intraspecific communication, that which occurs between members of the same species, is used to attract and recognize mates, to ward off an unwanted suitor, and to defend a territory or a morsel of food. Grasshoppers produce acoustical signals by rubbing the hindlegs against the tegmina (Fig. 12) or the sides of the abdomen. They may also communicate by rapidly flexing or snapping their hindwings in flight, a behavior called crepitation. Each species apparently produces its own unique sound and, in human terms, has its own language. The details, where known, of finding a mate are described in the species section of this guide.
Figure 12. Signals and postures commonly occurring in grasshoppers: (a) ordinary stridulation -- a slow, stereotyped, repetitive or non-repetitve, high amplitude movement in which the femur rubs against the forewing; (b) vibratory stridulation -- a fast, stereotyped, repetitive, low amplitude movement in which the femur rubs against the forewing; (c) ticking -- a stereotyped, repetitive or non-repetitve movement in which the tibiae are kicked out and struck against the ends of the forewings; (d) femur-tipping -- a silent, stereotyped, non-repetitve raising and lowering of the femora; (e) Femur-shaking (with substrate-striking) -- a stereotyped, repetitive shaking of the femora in which ends of the tibiae strike the substrate to produce substrate vibration or a drumming sound; (f) femur-shaking (silent or with wing-striking) -- similar to (e) but the movement os silent, or the femora strike the forewings; (g) femur-raising -- a slow, graded non-repetitive movement that may or may not be accompanied by mild upward kicking motions of the tibiae; (h) presenting -- a variable, graded posturing of the female in response to male courtship, in which the end of the abdomen is made more accessible to the male by lowering both the end of the abdomen and the hindlegs. (Courtesy of Otte, 1970, Misc. Publ. Mus. Zool., Univ. Michigan, No. 141.)
Oviposition behavior differs among species of grasshoppers. Most species lay their eggs in the ground. Females of some species choose bare ground, while others choose to lay among the roots of grasses or forbs. A female ready to lay often probes the soil several times before finally depositing a clutch of eggs. Experimental evidence indicates that probing is a means by which a female obtains sensory information on the physical and chemical properties of the soil. The ovipositor is supplied with a variety of sensilla that allow a female to monitor soil conditions. Temperature of the soil must be favorable, water content must be in a suitable range, and acidity and salt content of soil must be tolerable. Females of some species select loose soils such as sand, some rocky soils, while the majority of females prefer compact loamy soils for oviposition. The pods of different species vary in size, shape, and depth in the soil. The latter condition profoundly affects incubation temperature, hatching, and egg survival.
A female actively depositing eggs is often attended by one or more males. Depending at least partly on clutch size, females take from 25 to 90 minutes to lay a full complement of eggs. After withdrawing her ovipositor a female will take a minute or two to cover the aperture of the hole with particles of soil and ground litter. The female uses either her ovipositor or her hind tarsi, depending on species, to do this. The act appears to be instinctive maternal care that provides some protection for the eggs from predation by birds, rodents, and insects. In certain species, as soon as the female retracts her ovipositor, the attendant male mates with her; females and attending males of other species merely walk away from each other.
Grasshoppers have different ways of avoiding excessively high temperatures that may occur in summer for a few hours each day. When ground temperatures rise above 120½F, individuals of certain species climb plants, some to a height of only 2 inches on grass stems, others climb higher (5-12 inches), and some even higher on tall vegetation such as sunflower in the southern mixedgrass prairie or a tall cactus plant in the desert prairie. In these positions individuals usually rest vertically with the head up on the shady side of the plant. Many ground-dwelling species first raise up on their legs or stilt, but as temperatures rise further, they crawl into the shade of vegetation. Individuals of other ground-dwelling species may stilt, then move away from the hot bare ground and climb on top of a short grass such as blue grama. They face the sun directly so that the least body surface is exposed to the radiant rays. In this orientation the grasshoppers are 1 to 2 inches above ground and rays of the sun strike only the front of the head.
Characteristic behavioral responses regularly observed by grasshopper scouts and collectors of insects are the jumping and flying of grasshoppers, apparently to escape capture. The stimuli initiating these responses may be of many kinds but circumstantial observation indicates that movement of the collector's image across the compound eye is usually the primary stimulus. One may noisily push a stick on the ground close to an individual without eliciting a response. Also other insects, such as large darkling beetles or large grasshoppers, may crawl close and elicit no response until they touch a resting grasshopper. Phytophilous species of grasshoppers may not jump or fly to escape intruding scouts and insect collectors, but may shift their position away from the intruder to the opposite side of a stem, retreat deeper into the canopy, or drop to the ground. Collectors and scouts entering the habitat of dense populations of grasshoppers may get the impression of continuous movement by these insects, but investigation of their time budgets indicates that during most daylight hours they are largely quiescent (46 to 80% of the time). Considerably less time is devoted to feeding, locomotion, mating, and oviposition.
The adults of most species of grasshoppers possess long, functional wings that they use effectively to disperse, migrate, and evade predators. Adults regularly fly out from deteriorating habitats caused by drought or depletion of forage, but they may also leave a site for other reasons. Some individuals of a population instinctively fly and disperse while others remain in the habitat. The most notorious migrating grasshoppers are Old World locusts, Schistocerca gregaria and Locusta migratoria. Several species of North American grasshoppers are likewise notable migrators: Camnula pellucida, Dissosteira longipennis, Melanoplus sanguinipes, M. devastator, M. rugglesi, Oedaleonotus enigma, and Trimerotropis pallidipennis.
Past direct observations of grasshoppers in their natural habitat have revealed various behavioral responses among species. Each appears to have its own way of reacting to a battery of environmental factors. Because a relatively few species have been investigated, much remains to be discovered. The whole subject of grasshopper behavior provides a fertile area for research both in the field and in the laboratory. Acquiring sufficient information on the various aspects of grasshopper behavior will not only serve to improve integrated management of pest species and the protection of beneficial ones, but will also advance the science of animal behavior. Numerous observations of the behavior of common western grasshoppers have been made during the course of this study. Results of these observations are reported later in the treatment of individual species.
