specific as to the types of shrubs. Bootettix argentauu Brunerishost-specifictocreosotebush(Larrea tridentata [D.C.] Coville) and is found only where creosotebush occurs. Likewise,Aeoloplides species live only on plants in the family Chenopodiaceae. Grasshoppers that occur in particular habitats and feed on particular plants have adapted morphologically and behaviorally to live in their niicrohabitats. Uvarov (1977) proposed a series of grasshopper life forms that correspond to morphological features of grasshoppers that live in particular microhabitats. Four general life- form categories are applicable to most New Mexico grasshoppers: 1) terricoles that live on the bare ground surface, 2) herbicoles that live on forbs, 3) graniinicoles that live on grasses, and 4) arbicoles that live on shrubs and small trees. Many species do not fit entirely into one life-form type, but share characteristics of two. Because life-form attributes refler-t habitat and feeding prefer- ences, life-form morphology may be used as a tool to determine feeding habitats of grasshoppers from given areas. Behavior Grasshoppers, and Orthoptera in general, are well known for their behavior, particularly the sounds that they produce. Sound production and display flights in grasshoppers are behaviors associated with mating and territoriality. Grasshoppers do not sing or chirp like crickets and katydids because they do not have a file and scraper mechanism on their tegmina. Grasshoppers pro- duce sound by two mechanisms called stridulation and crepitation. Stridulation occurs when a grasshopper rubs the insides of the hind femora against the abdomen or tegrnina to produce a scraping or chirping sound; most grasshoppers produce sound by this method. The loud sounds produced by Syrbula and Booteuix are good examples of stridulation. Crepitation is sound produced by rapidly flexing the hind wings in flight producing crackling and snapping sounds. Crepitation is limited to the band-winged (Oedipodinae) and a few slant-faced (Gomphocerinae) grasshoppers. The crackling sounds produced byarphia and Tilmerotropis in flight are good examples of crepitation. Circotettix Tabula Rehn and Hebard is one of the loudest crepitating grasshoppers in New Mexico, producing loud snapping and rattling sounds. Stridulation andcrepitation sounds differ among different species, and like bird calls, can be used to identify different species of grasshoppers. Daily grasshopper activities are generally similar, but differ somewhat among different life forms in different habitats and center around thennoregulation, feeding, and mating. Most grasshoppers are active during day- light hours, and activity depends upon the amount of sunlight and temperature. Grasshoppers generally be- come active in the early morning and seek sunlight to increase their body temperatures. By late morning or midday they move about actively, feeding and engaging in mating activities. On hot days, activity usually de- creases from niid- to late afternoon, and grasshoppers often seek shade or perch on plants to avoid excess heat. It is likely that digestion occurs during this time. At dusk, grasshoppers generally seek resting places for the night, usually on vegetation. In warm area or at warm times of the year, many species of grasshoppers are active at night. Some species such as Booteuix will even continue to stridulate after dark. On warm summer nights one can find grasshop- pers wandering around on vegetation, often feeding. Few species fly at night, but some do. In southern New Mexico, Trimerotropispallidipennis is commonly seen flying around Ughts at night. Most grasshoppers probably do not move great dis- tances from where they hatched. Dispersal is common and accounts for most grasshopper movement over time. Grasshoppers are generally solitary except for mating behavior and move about independently. Rarely do grasshoppers actually become gregarious and nii- grate; however, swarming and migration occur in some species when population densities are particularly high. Migration is well known in species such as the desert locust (Schistocerca gregatia) and the migratory locust (Locusta migratoria) of Asia and Africa. In North America the only species of grasshopper that truly swarm and migrate are Melanoplus sanguinipes and rarely, Dissosteira longipennis (Thomas).Mese uligra- tion events occur only under unusually high population densities (Parker et al. 1955, Wakeland 1958). Population Dynamics Grasshoppers are well known for their variable popu- lationdensities,anditistheoccasionallargeincreasesin population densities that concern most people with agricultural interests. It is important to understand that not all species of grasshoppers have widely fluctuating population densities. Although all grasshopper popula- tions fluctuate in density over time, some fluctuate much more and reach higher overall densities than others (PWt 1977). Melanoplus sanguinipes, several other species of Melanoplus, Camnula pellucida (Scudder), Hesperotettix viridis, and Trimerotropis pallidipennis are New Mexico species that tend to have highly vari- able population densities from year to year and occa- sionally reach high densities in some areas. Most other species tend to remain at relatively lower densities, even though their populations may fluctuate considerably.