This is the first diary in the series to focus on a specific order of insects. As mentioned before, the function of these diaries are to serve as a companion to the excellent Bugguide website to aid backyard scientists in identifying the insects and other arthropods they may encounter. Accurate identification is necessary if we are going to monitor the effects of a changing environment.
I hearby declare the above to be the official theme song of this series.
I'm not going to tackle the insect orders in any particular sequence, just as the spirit moves me. I'm going to start with the Order Orthoptera. It's actually a largish order although dwarfed by the Coleoptera and the other really big ones. The Orthoptera seems like a manageable yet still significant starting point. Besides they are wicked cool - my first introduction to insects as a scientist. I'll try and stick in as much cool biology as I can.
The term Orthoptera is typically described as meaning 'straight wing'. Kossack marty35c, who is an expert in linguistics explains that pter actually meant something more like 'flight' in ancient Greek but has come to mean wing in biological names. As a descriptive name Orthoptera isn't all that great. While most grasshoppers and many katydids do have nice straight wings, crickets do not and many Orthoptera are wingless.
As I indicated in a bit of foreshadowing in the previous paragraph, this order comprises the grasshoppers, crickets, katydids, and their relatives. At least some examples of this order are presumably familiar to everyone reading this diary. Crickets are commonly found in or near our homes and we hear their calls routinely in the warmer months of the year. Grasshoppers are large common insects of yards and agricultural areas. But the order includes many other fascinating insects as well.
All of the Orthoptera have enlarged hind limbs. In particular, the hind femora (the long segments of the leg closest to the body)are large and powerful giving these animals the ability to jump considerable distances. The enlargement of the hind limbs is most extreme in wingless forms that rely on jumping to escape predators and least developed in burrowing species that don't need to jump. In species with wings the front pair of wings is thickened and leathery and known collectively as the tegmina. The hind pair of wings is membranous and used in flight. The back end of the abdomen has up to three projecting structures. The two on the sides are sensory structures known as cerci. They are found in both sexes but are fairly small and inconspicuous in Orthoptera other than crickets. The central projection is the ovipositor, a structure used to lay eggs, which is, not surprisingly, only found in females. The size and shape of the ovipositor is very useful in distinguishing groups of Orthoptera.
The Orthoptera are hemitmetabolous insects. This means that the immature stages closely resemble the adults but lack wings and reproductive structures. They are known as nymphs. In wingless species the nymphs closely resemble the adults.
Humans have long been interested in Orthopteran insects. They are large and also quite common in most parts of the world. Grasshoppers are important agricultural pests, with swarms of locusts plaguing farmers since before the dawn of civilization. Even the non-swarming species can be quite destructive.
On a more positive note Orthoptera are known for producing loud 'songs' many of which are considered pleasing, at least by some people.
For these reasons and others, members of the Orthoptera have been the subject of a great deal of scientific research. The list below is a partial compendium of interesting topics in Orthoptera research.
Swarming Behavior in Locusts Plagues of locusts are described in the bible and swarming behavior in locusts is well documented. The term locust refers to a variety of different grasshopper species that exhibit the swarming behavior. Swarming is a response to crowding and the locusts undergo behavioral and morphological changes as a result of interacting with other individuals. They then switch from solitary behavior to aggregating in enormous numbers and traveling long distances.
Color Variation A number of Orthoptera vary in color within a species. For example, many katydids have a green form and a brown form and the abundance of each form often varies seasonally. An extreme form of color variation occurs in the pygmy grasshoppers. Individuals often have fairly complex color patterns and these vary tremendously among individuals. It is thought that the color variation is a mechanism to avoid predators.
Wing Dimorphism Wing dimorphism in crickets and other orthoptera probably has a similar origin to the swarming behavior. In many cricket species, as well as pygmy grasshoppers and some other orthoptera, there are short winged and long winged forms. Short vs long refers to the length of the hind wings. In long-winged crickets the hind wings extend out from under the tegmina (front wings). Long-winged crickets are capable of flight but generally have fewer offspring.
Sexual Selection - Calling Most of the sounds made by Orthopterans are associated with mating in some way. The cricket sounds most commonly heard are males calling to attract mates. Males also call during aggressive encounters with other mates and they make quieter courtship calls to females who approach them. The simplicity of the signal and the ease of keeping crickets in the laboratory has made them natural subjects for the study of the male signal and female response. One interesting twist is the existence of non-calling males in populations. These 'satellite' males position themselves near calling males and attempt to intercept females. One cost to calling is a risk of parasitism. Parasitic flies in the genus Ormia are attracted to cricket calls and deposit larvae on the crickets with unpleasant consequences for the male concerned. Calling males are much more at risk of Ormia parasitism than either females or non-calling males.
There is a kossack connection here as our very own TexMex was involved in the research I describe in the above paragraph. There has been some more recent interesting work on a different cricket species that lives on many islands in the Pacific ocean as well as Australia. Marlene Zuk and her colleagues have shown that Hawaiian populations have recently come into contact with the Ormia flies and a mutation that makes it impossible for males to call is spreading in the population there.
Sexual Selection - Nuptial Feeding Orthopteran sex is a bit different than mammalian sex. Sperm transfer is accomplished by the male placing a sperm packet, called a spermatophore, onto the opening of the female reproductive tract. In many species there is an associated structure called the spermatophylax. This is generally a mass of protein. The female generally eats the spermatophylax and then removes the spermatophore. It is thought that the spermatophylax is a mechanism to delay removal of the spermatophore until the sperm have made their way inside.
In some species the spermatophylax is very large. In the Mormon cricket, Anabrus simplex (actually a kind of katydid), the spermatophylax can represent up to one third of the body mass of a male. This has resulted in a 'role reversed' mating system. Females will mate readily while males reject many potential mates. After a male mates it will require several days of feeding before he can mate again, a significant portion of an insect's lifetime.
Neurobiology of Calling and Response The simplicity of the cricket 'song' and the relatively large size of crickets (as insects go) have made them good subjects for studying the neural control of both the production of the call and the response to the call. I'm not (at all) a neurobiologist so I can comment further on this.
Crypsis and Background Matching Orthoptera are masters of camouflage. The more technical term is crypsis, as in cryptic. The variation in color, mentioned above, probably plays a role as it may prevent predators from learning to fixate on a single pattern when searching. Even without the variation grasshoppers and katydids in particular are remarkable mimics of stones, wood, and leaves, even including damage, discoloration, and fungal growth in their mimicry.
Identfication of Orthoptera
The information in the rest of the diary deals with the identification of Orthoptera to family or subfamily (in some cases). Identification of most Orthopterans you are likely to encounter to family is relatively straightforward. Some of the rare forms are a bit trickier. The boxes below take it in steps.
The Orthoptera are divided into two suborders. Identification of a specimen to suborder is a fairly simple matter in most cases based on the length of the antennae. Note the exceptions listed in the more detailed discussion of families.
If the antennae are around half the length of the insect's body or less then it is a member of the suborder Caelifera (grasshoppers and their relatives).
If the antennae are threadlike and are substantially more than half the length of the insect's body (in the majority of cases considerably longer than the entire body) then is a member of the suborder Ensifera (crickets, katydids, and their relatives).
Families of the Caelifera
The Caelifera are, for the most part, obviously grasshopper-like insects. Generally they are diurnal (active in the daytime). They have their tympana (ears) on the sides of their abdomens. The ovipositor (egg laying structure in females) is short and not very conspicuous.Acridid Grasshopper from Ecuador
There are five families in the suborder Caelifera in North America. One of the five is overwhelmingly more likely to be encountered than all of the others put together. This is the family Acrididae, often known as the short-horned grasshoppers. This is easily the largest family of Orthoptera and contains more species in North America than all of the rest of the order combined. You can basically assume that any that Caeliferan you encounter that doesn't match the descriptions of the other families listed below is a member of the Acrididae. A more detailed breakdown of the Acrididae is given in the next box.
The other Caeliferan family that is likely to be encountered is the Tetrigidae or pygmy grasshoppers. They are widespread and are certainly not rare. However they are small and found on the ground and are thus not as conspicuous as some other Orthoptera. As the same suggests they resemble miniature grasshoppers. They can be identified (and distinguished from the nymphs of grasshoppers from other families) by their pronotum. The pronotum is part of the exoskeleton that in most insects covers the top of the thorax. In the Tetrigidae the pronotum extends back over much of the abdomen, completely hiding the wings in short-winged individuals.Pygmy Grasshopper
The other three Caeliferan families are less likely to be encountered. The Tridactylidae are known as the pygmy mole crickets. This name is understandable as the Tridactylidae do resemble tiny mole crickets. However the two groups are not closely related and it is not really correct to refer to the Tridactylidae as crickets. If one is captured you should be able to see the modified front limb for digging. This in combination with the short antennae (and tiny size) will clearly distinguish them from any other Orthopteran. Pygmy mole crickets occur across the southern US and are usually associated with moist habitats adjacent to bodies of water. They are very small and are exceptionally powerful jumpers making them difficult to capture. When they leap they vanish right in front of your eyes.
The other two families are both wingless grasshoppers that, in North America, are restricted to desert and chaparral habitats in the southwest. They are the Eumastacidae and Tanaoceridae. They might be difficult to recognize. The Eumastacidae look just like a wingless Acridid grasshopper. Their hind legs often extend perpendicularly out from the sides of the insect. I have commonly seen members of this family in South America but not in the US. The Tanaoceridae have much longer antennae than other Caeliferans and could easily be mistaken for some of the desert katydids (other than being diurnal and having the wrong kind of ovipositor).Ecuadorian Eumastacid Grasshopper
Subfamilies of the Acrididae
This very large family has been difficult to organize into smaller groups and molecular evidence has led to a reorganization in recent years. Most of the species in North America belong to one of three large subfamilies. I will discuss these three groups and two smaller subfamilies.
Oedipodinae - Band-winged grasshoppers. As the name indicates the hindwings of these grasshoppers are colored and patterned. The wings are not visible except when the grasshoppers are in flight. Often make crackling sounds while in flight. Most commonly the tegmina (front wings) are mottled gray or brown. The head is rounded and the face is flat. Most common in areas with sparse vegetation.
Gomphocerinae - Stridulating slant-faced grasshoppers. These are slender grasshoppers with relatively short wings. They are mostly found on vegetation. The face is usually somewhat slanted although this can be fairly subtle and some species are not slanted at all. The term stridulating refers to the fact that the hind legs have a series of pegs that are used to produce sound.Gomphecerine grasshoppers mating
Cyrtacanthacridinae and Melanoplinae - Spurthroated grasshoppers. The Melanoplinae is the largest group of grasshoppers and highly variable in form and habitat. They can be distinguished from the two previous subfamilies by the presence of a large spine between the front legs (hence the common name). Mostly they have rounded heads and are slender. Some species have slanted faces and resemble Gomphocerine grasshoppers. The spur-throated grasshoppers do not make sounds in flight nor do they stridulate. The Cyrtacanthacridinae are similar to the Melanoplinae. They are relatively large grasshoppers and powerful fliers.
Romaleinae - Lubber Grasshoppers. This is a small group but conspicuous and distinctive. This group is similar to the spurthroated grasshoppers in having a spine between the front legs. The lubbers are very large, heavy-bodied insects. They have short wings and cannot fly.
Classification and Identification of the suborder Ensifera
The Ensifera suffer from a very unstable classification where grouping vary quite a bit from source to source. As always I will use the Bugguide classification to make things easier for readers.
The Ensifera are largely nocturnal animals although there are quite a few exceptions. In addition to their long antennae they have long slender ovipositors (sometimes longer than the body of the insect). The species that have tympana (ears) have them on their front legs. Many members of this suborder are known for producing loud mating 'calls' at night. The sounds are produced by fine-toothed structures on the front pair of wings.
The Ensifera are divided into two infraorders - the Gryllidea (crickets) and the Tettigoniidea (katydids, camel crickets and a variety of other amazing critters). The Gryllidea can usually be identified by the following characteristics: the cerci (paired sensory structures at the back of the abdomen) are large and obvious, the ovipositor is (usually) tube shaped, and the wings (when present) are folded flat over the insect's back. The Tettigoniidea can be recognized by having proportionately much smaller and inconspicuous cerci, a blade shaped ovipositor, and wings (when present and large) held rooflike over the back of the insect (similar to grasshoppers).
The most likely problem in identifying a specimen is likely to come from a specimen that is either wingless or has very short winged. The majority of wingless species are in the Tettigoniidea. However there are quite a few wingless and short-winged species in both groups (the wings don't cover the entire abdomen) and in such cases the position of the wings is not useful and the cerci and ovipositor (obvious but only in females) are more useful.
In general the Gryllidea are smaller species than the Tettigoniidea. If you are sure you have an adult then anything much over an inch long (not counting antennae, ovipositors, etc.) is almost certainly a Tettigoniidea and anything less than half an inch long is almost certainly a Gryllidea. However this should be used very cautiously as it may be very difficult to distinguish adults from juveniles given the large number of wingless species. See the next two boxes for a breakdown of each group.
Families and subfamilies in the GryllideaThere are four families: three small and one large.
Gryllotalpidae - Mole crickets. These are mid-sized (similar to a house cricket) insects with enlarged front limbs for burrowing. The hind limbs are only very slightly enlarged. Unlike other burrowing Ensifera the mole crickets are fully winged. Native species are almost completely restricted to the eastern and central parts of North America but an introduced species is found in Arizona and California, presumably mostly in landscaped environments (these are moisture loving animals). They superficially resemble the Pygmy Mole Crickets but are much larger.
Myrmecophilidae - Ant crickets. Very small wingless crickets that live in ant colonies. These are the smallest orthopterans in North America - smaller than a fruit fly!
Mogoplistidae -Scaly crickets. Small wingless crickets that live on bushes or the ground, primarily southern in distribution.
All other North American crickets are in the family Gryllidae. This is a large and diverse group which includes the familiar house and field crickets as well as other types of crickets. The Gryllidae has several distinctive subfamilies.
Gryllinae - House and field crickets. These are what most of us think of when we think of crickets. The house crickets you buy in the pet store or the field crickets you find in your yard or coming into your house. The majority of the native species are in the genus Gryllus. In addition to their value as food for a variety of exotic pets, field crickets have been used extensively in research in animal behavior, neurobiology, and evolution.
Nemobiinae - Ground crickets. These closely resemble the field crickets but are quite a bit smaller. All are half an inch long or less whereas most of the Gryllinae are well over half an inch long. As the name indicates they are usually found on the ground, often in grass.Ground Cricket
Oecanthinae - Tree crickets. These are slender insects that are usually at least partly pale green in color. They are found in vegetation including larger herbaceous plants, shrubs, and trees. They are heard much more often than they are seen. Many of the species have quite loud calls and can call in large numbers.
Trigonidiinae and Hapathinae - Bush Crickets. Small crickets (1/4 to 1/2 inch long) typically found in shrubs and low vegetation. The Trigonidiinae have blade shaped ovipositors unlike the other crickets. The Hapathinae are more commonly called Eneopterinae in other sources. Smaller and less conspicuous than the tree crickets.
Classification of the Tettigoniidea
There are six families in this group in North America. Both on this continent and world-wide this group contains some large and spectacular insects. Because they are mostly nocturnal it requires some effort to encounter them.
Four of the families in North America are wingless and a fifth has species with very short wings. The largest family, the Tettigoniidae contains species with a range of wing sizes.
Anostostomatidae - I don't think there is an appropriate common name for these guys in North America. This family is predominantly from the southern hemisphere and includes the famous Wetas of New Zealand. In North America this group is restricted to coastal California and the Channel Islands. The American species resemble Camel Crickets but have a flat back rather than the humped back of the Camel Crickets.
Prophalangopsidae - Heavy-bodied insects with a rotund abdomen and relatively short hind legs. The wings are short but males do call with them to attract mates. In a novel case of feeding your 'date' females eat the fleshy hind wings of the males while mating. This is an ancient group with very few species world wide. The three North American species occur in the montane west ranging from northern New Mexico to central BC. Most commonly found in coniferous forests but also in high desert.
Gryllacrididae - The single North American species is a wingless insect found in the eastern US north to southern New Jersey and central Missouri. It also resembles a flat-backed Camel Cricket. It shelters in the day in rolled up leaves held together by silk. Antennae are extremely long.
Stenopelmatidae - Jerusalem crickets. These are large, robust, wingless, burrowing insects with a rotund abdomen and powerful front limbs for digging. They are impressive in appearance and widespread in western North America although their burrowing habits mean they are not seen all that often. The number of species is uncertain but may be as high as 60.
The last two families have many many species each and occur almost everywhere in North America outside of arctic regions.
Rhaphidophoridae - Camel Crickets. This is a very large family but most of the species have the same basic appearance. They are wingless with very long hind legs and very long antennae. The back is highly arched giving the humped appearance from which they get their name. Apparently they will live in houses all though I have never experienced this myself. Many species live in caves or on sand dunes.Camel Cricket
Tettigoniidae - 'Katydids'. This family has at least three widespread English names all of which leave something to be desired. Katydid is the most common name in North America and is derived from the call of a widespread species in the eastern US. Given that the vast majority of species in the family don't make a 'katydid' call it is understandable why non-North Americans might not take to this name. In British English they are called Bush-crickets which isn't much better as they are definitely not crickets and quite a few of them are not found in bushes. The third name is long-horned grasshopper. Although definitely not closely related to the Acrididae, many of the Tettigoniidae are more grasshopper-like in appearance than most Ensifera.
This is a large and diverse group. Bugguide divides them into six subfamilies. Two of these are quite small (one is a single introduced species) and I will ignore them. Three of the other four subfamilies are grasshopper-like with large wings held roof like over their backs. Most members of these three subfamilies are green in color and found up in vegetation although some species have brown (or pink!) color variants. The fourth subfamily mostly contains short-winged flightless species although it has some grasshopper like forms.
Conocephalinae - The name literally means cone-head and this is an accurate term as all the members of this group have a head that comes to more or less of a point. Formerly broken into two subfamilies and still described that way in most sources. The wings are long and straight. Usually found in tall herbaceous vegetation (tall grasses, etc.). The Meadow Katydids have only a slight point to their head and are small to medium sized. They resemble a short-horned grasshopper with long antennae and frequently call during the day as well as at night (they have calls composed of buzzes and clicks). The Cone-headed Katydids are large insects with a head that comes to a very definite point. Their calls are very loud. They are strong fliers and will bite readily if given a chance.Meadow Katydid
Pseudophyllinae - 'True' Katydids. The name means false leaf. This is one of two subfamilies in which the wings often resemble leaves. In tropical species the wing mimicry can be quite remarkable. There is only one widespread species in North America, the common true katydid, Pterophylla camelifolia. They can be commonly heard calling in eastern North America, at night during the warmer part of the year. In the north the call sounds like 'katydid' or 'she-did'. In the south the call has more 'syllables' and is faster. Although almost anyone within the species' range will have heard its call they are seldom seen as they spend their entire lives high in trees.Common True Katydid
Phaneropterinae - Sometimes known as the false katydids which is a bit unfortunate because, at least in North America, they are more widespread and commonly encountered than the 'true katydids'. This is a common and diverse group. In general they are somewhat more slender-bodied than the other subfamilies and some species are very slender and long-legged indeed. Their wings are often leaf like, although some species have narrow wings. Unlike the Pterophyllinae these katydids have hind wings that extend back further than the front wings, projecting backwards and coming to a point. Their calls are usually quiet clicks or lisps which can be quite complex in some species. Mostly found in weedy vegetation or shrubs but some are found in trees.Greater Angle Wing Katydid
Tettigoniinae- Shieldbacks. Most members of this subfamily have very short wings that are hidden by the pronotum (top of the thorax). They are flightless but capable of producing calls. Other species have full sized wings and are grasshopper-like. Most common and diverse in the west but found throughout North America.Robust Shieldback
This order has a lot identification resources available.
On the web
Singing Insects of North America. A great web site for katydids and crickets with range maps, photos, and recordings of their songs. Not useful for grasshoppers or any non-calling Orthoptera.
Orthoptera Species File. Really a web site for professional taxonomists with a lot of detail on names, classification, and distribution.
Songs of Insects. Web site for the book mentioned below. Has a lot of information in its own right.
USDA Grasshopper Website. There are a number of agriculture sites with grasshopper info. This has a section with links to guides to various regions of the US. The emphasis is on the west, especially on rangeland species but there are guides to other areas such as Florida and Wisconsin.
Field Guide to Grasshoppers, Katydids, and Crickets of the United States. 2004. John Capinera, Ralph Scott, and Thomas Walker. Cornell University Press.
This book was written by experts on the different groups of Orthoptera. It has range maps and color plates (not of every species covered). It is particularly good for grasshoppers and katydids and not as good for the less conspicuous members of the order (Pygmy Grasshoppers in particular I thought were slighted).
The Songs of Insects. 2006. Lang Elliot. Houghton Mifflin. A beautiful recent book with great photography. Comes with a CD of songs as well as the excellent web site. Katydids and crickets only with an emphasis on eastern species.
How to Know the Grasshoppers, Crickets, Cockroaches and their Allies. Jacques Helfer. Originally part of the Pictured Key Nature Series published in 1952. Second Edition reprinted by Dover Press in 1987. I snapped one up when I found it in a specialty bookstore in Chicago in the early 90s. This is my favourite Orthop guide. The taxonomy is out of date and there are no photographs, only line drawings (both realistic ones and more whimsical ones). But it can be used to identify almost 800 species of Orthoptera and about half a dozen other small orders (over twice as many as the Capinera guide above). A great resource that is technical enough to be useful for someone serious about identification but written for non-entomologists.