Identification
Mostly relatively slender, medium-sized (mostly between about 1 and 2 inches long). The pronotal ridge is cut twice, usually faint or entirely absent on the posterior half of the pronotum (metazona). The front wings have dark markings, usually dark cross bands that may be clear and well-defined or made of aggregations of small irregular dark spots. Hind wings with the basal portion colored yellow, green, or blue (never reddish colors), and usually with a dark cross band that has a spur extending toward the base of the wing near the front edge. Hind femora usually with at least faint diagonal crossbands externally, and perpendicular light and dark banding on the inside (in some mostly light or dark). Hind tibia varies in color with the species (brownish, blue, green, yellow, orange, red, or rarely purplish), and can be useful for species identification.
(1)
Circotettix species have wider (often long) tegmina; hind wings very wide with the outer edge often undulate, apex in most produced, and with at least some of the radial veins very strongly thickened. Hind tibiae are never reddish.
Spharagemon species mostly have the top of the pronotum less flat (more roof-like) with the median ridge raised more (often forming a crest) and only cut once (sometimes notched a second time, but mostly not). Dissosteira differ similarly, plus have distinctly different wing coloration.
Conozoa are best distinguished by a combination of traits and by comparing individual species; most characteristics of the genus are shared with at least some species of Trimerotropis. They run smaller and more slender on average, with the dark cross bands of the tegmina (front wings) usually not crossing the top when folded. The rear lower angle of the sides of the pronotum is most often produced downward into a sharp angle or tooth. Some Conozoa, but not all, have a once cut pronotal ridge.
Microtes species are very limited in distribution (near the Pacific Coast), and average smaller, a bit squatter (dorso-ventrally flattened) with shorter wings. They tend to be rather fuzzy. [see also Trimerotropis helferi]
Remarks
As currently defined, this is the largest American genus of Band-wing Grasshoppers, and there is a wide range of variation in appearance, size, and behavior. They can be found in nearly all habitats that are sunny, relatively dry, and have bare ground or rocks exposed. There are few species in the East and many in the West. They are very closely related to a few other genera (most notably Circotettix, Spharagemon, Conozoa and Microtes), and it is likely that limits of the genus will be redefined as more is learned about how various species are related to one another.
All species can produce noise during flight (crepitation), and often the pattern and nature of the sound produced can help identify species.
Trimerotropis as currently defined can be divided into two major divisions, based primarily on chromosome structure.
Based on a number of traits (including characters of chromosomes, morphology, coloration, behavior and sound, ability to hybridize, etc.), most species can be further arranged into groups of close relatives. It is quite likely that in the near future, some of these groups will be divided among separate genera, but for now they are all called Trimerotropis.
Those groups of species listed in the first division of Trimerotropis have or are suspected of having chromosomes like those typical of most other grasshoppers, and also share a typical chromosome number of 2n=23 (males) or 2n=24 (females). They are likely (all or at least most) more closely related to Spharagemon, Conozoa, and perhaps Microtes than to the species groups listed in the second division. There are no species with blue hind wings included here, though some can be a bit greenish, sometimes with bluish main veins (especially toward the base). This has been called the "Section A" in some publications.
Those very closely similar to Spharagemon (differing only in the second notch in the mid pronotal ridge) include: T. pistrinaria, modesta, and tolteca. The closely related species "Trimerotropis" campestris has already been moved to Spharagemon, and probably all of these should be so treated. In flight these produce a loud and moderately harsh continuous buzz, and tend to fly in a relatively straight or evenly curved path. All of these normally have orange to red hind tibiae (rarely yellow). "Spharagemon" bunites from the Sierra Nevada in California may belong with this group too, but it has blue hind tibiae and has been little studied. It has been considered as close to S. campestris.
T. latifasciata and T. melanoptera are closely related and fairly similar to both the previous and next groups. In flight these produce a loud and moderately harsh interrupted buzz, and they tend to turn and zig-zag in a low rapid often long flight. The unnamed "species B and C" listed on BugGuide probably are most closely related to these, but seem to have less loud and harsh crepitation. All four have orange to red hind tibiae.
Those apparently most closely related to the type species of Trimerotropis (T. maritima), are T. agrestis, californica, pacifica, and titusi. In flight these produce a loud and moderately harsh continuous buzz, and tend to fly in a relatively straight or evenly curved path. In restricted habitats they may fly shorter distances and may turn back to near where they started from. All of these have yellow to red hind tibiae. There is a strong tendency in all of these to have a tooth or a projection at the lower rear angle on each side of the pronotum.
T. albescens, arenacea, & whitei are small species, very similar to one another, and perhaps closely related to the the previous or to the next group. These produce a moderately loud and harsh buzz, but (perhaps due to small size) not as loud as the previous group. These have blue, blue to yellow, and yellow to red hind tibiae respectively, and seem to form a cline of continuous variation from west to east (probably all one species).
Species very similar to those of the first group and to Spharagemon, but smaller, with hind tibiae yellow to (mostly) blue. Flight crepitation not quite so loud and harsh and somewhat more rapid, continuous during direct flights, but sometimes interrupted during short leasurely flights and courting displays. Includes T. bifasciata, T. inconspicua, and T. topanga. These smallish species with blue hind tibiae are a bit problematic, because they are also similar to the T. cincta group, and there is some evidence that they can perhaps hybridize with certain members of that group. They are morphologically very close to the first group listed above and to Spharagemon, and have similar crepitation. In it's southern range T. topanga approaches T. californica in characteristics, and it has been associated with that species due to the presence (sometimes) of a tooth on the lower margin of the lateral lobes of the pronotum. There is evidence that T. inconspicua may blend or hybridize with T. pistrinaria in New Mexico and Utah. In some ways this group is also similar to the T. arenacea group (small size, similar crepitation, yellow to blue hind tibiae, etc.). Perhaps "Spharagemon" bunites (with blue hind tibiae) belongs here, but it has been little studied so far.
Forming a seemingly close knit group are: T. cincta, fontana, infantilis, koebelei, occidentaloides, occulens, and santabarbara. These [apparently all?] produce a rapid, not harsh buzz or interrupted buzz in flight, they tend to make unexpected, often upward directed turns in flight, and most will fly into or through trees and brush. These all have blue hind tibiae, mostly black at the very base with a pale ring next to the black, often dark at the tip too. The relationship of this group to some of the species mentioned above with blue hind tibiae may be close, but this is not clear. There may also be a close relationship to Conozoa.
note: In early literature, there was much confusion between various species of Trimerotropis and Spharagemon with red hind tibiae, and older records for several species are often questionable; many records are definitely based on misidentified specimens.
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All of those species listed below, where known so far, share certain modifications of chromosomes with Circotettix, and as in that genus, many (not all) have a reduced chromsome number due to a fusion of two chromosomes per set into one, resulting in 2n=21 (males) or 2n=22 (females). Thus, these species are probably very closely related to one another and to Circotettix. Yellow, green, and blue hind wing colors are all common, with some species variable in color. None of these have orange or red hind tibiae. This has been called the "Section B" in some publications.
Those very closely akin to Circotettix (and probably better placed in that genus) include: T. bernardi, cyaneipennis, fratercula, leucophaea, sparsa, verruculatus, the unnamed "species A", and probably T. gracilis. T. arizonensis looks a lot like T. cyaneipennis, but has certain traits in common with T. saxatilis; to which group it belongs needs more study. Most of these crepitate with a moderately loud and harsh crackling made up of rapid separate bursts of two or three snapping sounds each (except T. gracilis which ticks loudly, and T. arizonensis which has a less harsh interrupted buzz). Most tend to have a rather direct flight when startled, but when not disturbed many bounce and zig-zag around when they fly, and the males of most of these species will hover or bob around in the air and crepitate in much the same fashion as Circotettix species. Hind tibia color in this group varies through yellow, green, blue, brownish, or black. The species T. gracilis from the Rocky Mountains and Colorado Plateaus, needs to be studied cytologically, and also shows close similarities to certain Conozoa. It's placement here is tentative, but it is very simlar in appearance and morphology to "unnamed species A" from the Great Basin, with which it has been badly confused (and which has been studied cytologically)
T. inyo, lauta, occidentalis, thalassica, and maybe "Spharagemon bunites" are only somewhat similar to, but perhaps closely related to the previous group. Together they may form a natural grouping of related species, but likely not all of them. Several of them are poorly studied. Most (?all) produce a less harsh more rapid interrupted "buzz" or "crackle" than species of the previous group (unreported in S. bunites). Mostly, these have blue hind tibiae.
Those species apparently close to T. pallidipennis include: T. huroniana, pseudofasciata, salina, saxatilis, schaefferi, and perhaps T. arizonensis. In flight they produce a relatively loud, but not particularly harsh, fast but interrupted buzz, with the pulses varying from three or four to several ticks each. Where the habitat is extensive they tend to have long direct flights when disturbed. Those from restricted habitats tend to not fly long distances and often turn back on their previous path. Even so, it is usually a rapid direct flight. Males tend to be almost hyperactive and make frequent short flights when not disturbed, but rarely (if ever?) do high acrobatic aerial displays. Hind tibiae are yellow (sometimes brownish), and hind wings yellow (often greenish toward base), except in T. pseudofasciata with bluish wings and tibiae most often blue; and, in T. arizonensis light greenish to light blue wings and tibiae.
T. helferi is an odd bedfellow in Trimerotropis, and is morphologically much like Microtes. It has chromosome structure similar to "Section B" of Trimerotropis and Circotettix, implying a close relationship. However, based on both morphology and behavior it seems possible that the chromosome structure is a coincidence, that the species may be misplaced in Trimerotropis, and that it should perhaps belong in Microtes, where it was placed by Otte (1984).
Print References
'American Insects: A Handbook of the Insects of America North of Mexico'
(1), p. 173
'Grasshoppers of Florida'
(2), pp. 74-75
'The North American Grasshoppers' vol. II
(3)
Weissman, David B. & D.C.F. Rentz, 1980. 'Cytological Morphological, and Crepitational Characteristics of the Trimerotropine (Aerochoreutes, Circotettix, and Trimerotropis) Grasshoppers (Orthoptera: Oedipodinae)', Transactions of the American Entomological Society 106: 253-272
Rentz, D.C.F. & David B. Weissman, 1984. 'Five New Species of the Band-winged Grasshopper Genus Trimerotropis Stål (Orthoptera: Oedipodinae)', Pan-Pacific Entomologist 60(2): 227-237
Weissman, David B., 1984. 'Notes on the Autecology, Cytology, Morphology, and Crepitation of Trimerotropis Grasshoppers (Orthoptera: Oedipodinae)', Pan-Pacific Entomologist 60(4): 269-278
