Insect Orders 1
Orders of Insects (Groups 1 – 6)
Hexapoda is a group of arthropods characterized by, among other things, the possession of three pairs of legs (six total, hence the name: hex, six; poda, legs).[1] The vast majority of hexapods are insects, but some small groups that are related to insects have six legs but are not quite insects. This section will briefly cover all the orders of hexapods (Insect Orders, above) but much more detail can be found about each major order in later First Detector Entomology pages.
Several important resources about insects include the following books: Borror and Delong’s Introduction to the Study of Insects[1], Evolution of the Insects[2], and Soil Biology Guide[3]. These were used so extensively within this section they will not be cited separately.
1. Non-Insect Hexapods
Body plan: three main body segments, three pairs of legs, applies to all of the following insects
Mouthparts: entognathous (withdrawn), applies only to these three orders
Life cycle: ametabolous
Wings: none
Order Protura
Protura are small 1.5 mm long soft bodied hexapods that live in soil. They are the only order of hexapods that lack true antennae, however they have elongate antenniform forelegs. The mouthparts of Protura are entognathous, recessed within a cup-like extension of the gena (the "cheek" area of the head). Protura are the only order of hexapods with anamorphic development, where body segments are added with each molt. The life cycle of Protura is ametabolous: egg, pre-larva (9 body segments), larva I (9), larva II (10), maturus junior (12), then A) female adult (12), or B) preimago (12), male adult (12). There are three families and ~73 species of Protura known from North America North of Mexico. Triplehorn and Johnson (2005) is a good resource for information about this order.
Order Collembola (Springtails)
Collembola are small soft bodied hexapods. They possess true antennae and have entognathous mouthparts. Collembola are the only order of hexapods with a collophore, a structure found on the ventral side of the first abdominal segment used for water uptake and excretion. They jump using a furcula, an elongate forked appendage which arises from the ventral side of the 4th abdominal segment. When bent beneath the body the furcula is clasped by the retinaculum which is located on the ventral side of the 3rd abdominal segment. Some families of Collembola lack a furcula.
Collembola have epimorphic development, they have the same number of body segments throughout their life. The life cycle of Collembola is ametabolous: egg, multiple instars, adult. Collembola feed on decaying plant and animal matter, other detritus, and fungi. They can live at densities of 100,000 per square meter and are occasionally pests in green houses and mushroom cellars. There are 12 families and ~812 species of Collembola known from North America North of Mexico. Triplehorn and Johnson (2005) is a good resource for information about this order.
Order Diplura
Diplura are small (less than 7 mm), pale, elongate hexapods that are immediately recognizable due to their possession of two caudal filaments. Two families, Japygidae and Parajapygidae have short one segmented caudal filaments that they use as pinchers similar to Dermaptera (earwigs). Diplurans can be easily told apart from dermapterans by their smaller size. The life cycle of Diplura is ametabolous: egg, multiple instars, adult. Dipluran feeding habits are poorly known, presumably they feed on detritus and other dead organic matter. They are generally found in damp soil, rotting logs, in caves, and other moist places. There are four families and ~125 species of Diplura known from North America North of Mexico. Triplehorn and Johnson (2005) is a good resource for information about this order.
2. Apterygote Insects
Mouthparts: ectognathous (exposed), applies to all of the following insects
Life cycle: ametabolous
Wings: none
Order Microcoryphia (Jumping Bristletails) (Archaeognatha of older texts)
Microcoryphia are elongate, scale covered insects with ectognathous (exposed) mouthparts, one pair of cerci (cercus, singular), and a median caudal filament. They can grow to about 15 mm in length. Characters that can be used to distinguish Microcoryphia from the superficially similar looking order Thysanura are: large contiguous eyes, a humped back, and jumping when disturbed. Microcoryphia are unusual in their ability to molt even after they have reached adulthood (up to 50 times) these are referred to as "senile" adults. Microcoryphia have an ametabolous life cycle: egg, multiple instars, adult, and senile adults. They must cement themselves to a solid substrate in order to molt successfully, so do not keep your pet Microcoryphia in a sandy aquarium. Microcoryphia feed on algae, lichens, detritus, and other moist organic matter. There are two families and ~24 species of Microcoryphia known from North America North of Mexico. Triplehorn and Johnson (2005) is a good resource for information about this order.
Order Thysanura (Silverfish)
Thysanura are elongate, slightly flattened, scale covered insects with one pair of cerci, and a median caudal filament. Their small eyes, flattened body (as opposed to humped), and running behavior (rather than jumping) help to distinguish them from the Microcoryphia. Thysanura can grow to be about 19 mm long. Two members of this order are synanthropic, associated with humans and the artificial habitats we create. One is the Silverfish, Lepisma saccharina Linnaeus which is covered in silver scales and feeds mainly on starch and items that contain starch such as books, starched clothing, paper, etc. The Firebrat, Thermobia domestica (Packard) is tan or brown colored and is often found near warm places such as furnaces, boilers, etc.
Thysanura have an ametabolous life cycle: egg, multiple instars, and adult. Those not associated with humans live in termite or ant colonies, caves, mammal burrows, or in the soil. There are three families and ~20 species of Thysanura known from North America North of Mexico. Triplehorn and Johnson (2005) is a good resource for information about this order.
3. Pterygota
Adults possess wings, or if wingless, is evolved from an ancestor with wings, applies to all of the following insects
Wing type: Paleoptera (non-folding), applies only to these two orders
Life cycle: hemimetabolous
Order Ephemeroptera (Mayflies)
Mayflies are elongate, medium sized (10-50 mm), soft bodied insects. Adults have triangular wings and three caudal filaments, although the middle filament may be reduced in some species. All immature mayflies in North America are aquatic. They are easily recognizable by their three caudal filaments (only two in some species) and single tarsal claw. Plecoptera (stonefly) immatures, which look similar, have two tarsal claws. Immature mayflies may be found in a wide variety of habitats from lakes and ponds to rivers and streams, and fill a wide variety of niches from grazers and scrapers to filterers and active predators. Many immature mayflies are intolerant of various types and kinds of pollution and can be useful indicators of human caused disturbance. Mayfly immatures and adults are very important food for fish, birds, and other wildlife.
Mayflies have a hemimetabolous life cycle with a unique additional step called a subimago (imago meaning "adult"). Beginning at the egg, a mayfly hatches to an immature that grows and molts many times. The immature then molts into a subimago, a winged immature that tends to be duller in appearance, hairier, and with shorter appendages than the adult. The subimago lacks developed genitalia. After a short flight the subimago lands and molts into the adult. Adults live from hours to days and lack working mouthparts. In some cases there are mass emergences that may be used to overwhelm predators. In some families males swarm and fly up and down in unison, and males may have specialized upward pointing turbinate eyes to better see females in the swarm.
There are 21 families and ~599 species of Ephemeroptera known from North America North of Mexico. Merritt et al. (2008)[4] is an important reference for adult and immature identification of this order.
Order Odonata (Dragonflies and Damselflies)
Odonata are medium to large (2.2 – 10 cm) insects with large eyes, two pairs of membranous wings, and an elongate abdomen. There are two suborders in North America, Anisoptera (commonly called Dragonflies) and Zygoptera (Damselflies). Dragonflies tend to be larger, have close-set eyes, the base of the hind-wing wider than the base of the fore-wing, and have stouter abdomens. Damselflies tend to be smaller, have wide-set eyes, fore and hind wings of similar shapes, and have long thin abdomens. Immature damselflies have external caudal gills at the end of the abdomen, which are lacking in immature dragonflies.
Immatures of both suborders are aquatic, with a few rare exceptions. They superficially resemble their adult counterpart but lack fully formed wings. Immature odonates can be immediately recognized by their unique mouthparts. The two basal segments of the labium are elongate to produce a double hinged arm, which, when retracted folds on itself and rests under the body of the insect. The labial palps are modified into lobes which may bear hooks, teeth, and/or raptorial setae. Prey capture is achieved by extending the labium, grasping the prey with the palpal lobes and retracting the labium. This anatomy can be easily demonstrated if you imagine your arm at the shoulder is your lower lip, put your elbow straight down against your chest, and cover your mouth with your hand. Extend your arm out to grasp a prey item, then as you pull your elbow back to your chest, and put your hand back over your mouth.
All adult and immature odonates are predatory and Odonata is the only order in which all adults (male and female) have wings. Odonates have a hemimetabolous life cycle: egg, multiple immature instars, adult. The final instar leaves the water, crawls up trees, bridges, emergent vegetation, etc. and molts into an adult (eclosion), leaving behind the exoskeleton of the final instar (called an exuvia). In some species adults defend territories and engage in elaborate mate guarding behavior.
Adult and immature odonates eat other adult and immature insects, including mosquitoes. Their usefulness as bio-control agents is unknown. Dragonflies cannot "sting" nor will they sew shut the mouths of children who talk too much. Odonates are largely beneficial or innocuous. There are 11 families and ~435 species of Odonata in North American North of Mexico. The field guide by Dunkel (2000)[5] covers all North American dragonflies, and numerous other regional field guides exist. Important references on Odonata include: Corbet (1999)[6], Merritt et al. (2008)[7], Needham et al. (2000)[8], Tillyard (1917)[9], and Westfall and May (1996)[10].
4. Neoptera
Neopterous insects have wings and the specialized anatomy needed to fold their wings flat over their backs. This may seem trivial, but it’s difficult to crawl under something for food or protection with your wings sticking out to the side or up in the air. Some insects don’t have wings (e.g., fleas) but are still in this group because their ancestors had wings.
Wing type: Neoptera (folding), applies to all of the rest of insects
5. "Orthopteroid" Insects
The "Orthopteroid" insects are a group of seven orders (see below) that share numerous characteristics that make them superficially similar to each other. Most of the members have a foreword projecting head (prognathous) with biting/chewing mouthparts. The cockroaches have biting/chewing mouthparts but have a rear facing head (opisthognathous) that is covered by the pronotum. All of the members of this group have a hemimetabolous life cycle. Members of this group may be predatory, plant eating (phytophagous), or eat detritus (detritivorous).
| Order Name* | Common Name |
|---|---|
| Orthoptera | Grasshoppers and Crickets |
| Mantodea | Praying Mantids |
| Blattodea | Cockroaches |
| Isoptera | Termites |
| Phasmatodea | Walking Sticks |
| Grylloblattodea | Ice Crawlers |
| Mantophasmatodea | African Rock Crawlers |
*Note: Over time different authors have interpreted these groups in different ways, for example: some authors group all grasshoppers, mantids, cockroaches, and walkingsticks under "Orthoptera"; other authors group mantids, cockroaches, and termites in one order called Dictyoptera; some authors even split grasshoppers and crickets into two different orders. Recent data suggest that termites should be included with roaches as a part of the Blattodea. The above arrangement is one of the most widely used.
Order Orthoptera (Grasshoppers, Crickets, and Allies)
Orthoptera are small to large insects (~7 – 90 mm) that are most easily recognized by hind legs modified for jumping (with an enlarged hind femur) and a large pronotum. Orthoptera have biting/chewing mouthparts and a hemimetabolous life cycle. Most Orthoptera have a long ovipositor, used for laying eggs, and two pairs of wings that are held folded over the back.
Orthoptera is divided into two suborders:
Caelifera ("short horned grasshoppers") generally have antennae that are shorter than the body. The suborder contains the grasshoppers, pygmy grasshoppers, and pygmy mole crickets.
Ensifera ("long horned grasshoppers") generally have antennae that are longer than the body. The suborder contains Jerusalem crickets, cave or camel crickets, katydids, crickets, and mole crickets. Mole crickets lack long antennae, but can be easily recognized by their enlarged front legs which are used for digging.
There are 16 families and ~1210 species of Orthoptera in North American North of Mexico. The field guide by Capinera, et al. (2004)[11], and especially Helfer (1987)[12] are important references on this order. More information about Orthoptera within the First Detector Entomology Wiki can be found here.
Order Mantodea (Praying Mantids)
Praying mantids are medium to large (100+ mm) predacious insects with raptorial (grasping) forelimbs. Generally mantids have a very elongate pronotum, although in some tropical species the pronotum is short and the mantid superficially looks like a fancy cockroach. Mantids are visual predators and can rotate their heads to "look over their shoulders" as they search for prey. The femur and tibia of the forearm are festooned with spines that help to grip and subdue prey. Mantids have biting/chewing mouthparts.
Praying mantids are hemimetabolous. The female places an egg case, called an ootheca, which may contain up to several hundred eggs, on a limb or piece of grass. After overwintering, the eggs hatch and young emerge. Praying mantids will cannibalize if given the opportunity. Immatures grow through 4-12 instars before becoming an adult.
Although praying mantids are advertised as good "biological control" the impact they have on garden pests is probably negligible. Pest populations, especially those that can travel long distances, will probably arrive in a garden at a rate much higher than a mantid can eat. Additionally, mantids generally do not discriminate between insects that a gardener considers a "pest" or a "beneficial". Mantids can become a nuisance around bee hives. If you don't raise bees, there is really no good reason to discourage mantids in your yard and garden.
There are 2 families and ~30 species of Mantodea known from North American North of Mexico. Helfer (1987) and Triplehorn and Johnson (2005) are good resources for information about this order.
Order Blattodea (Cockroaches)
Cockroaches are small to large (3 – 50 mm) insects that have a pronotum that conceals the head and a distinctive oval body shape. Cockroaches have biting/chewing mouthparts, generally eat detritus, and usually have two pairs of wings, although these may be reduced in adults. Most cockroaches are tropical and want nothing to do with humans whatsoever. However, there are a few species of cockroaches that really appreciate the wonderful homes we make for them and all the food we give them. At least that's how they see it.
Cockroaches are hemimetabolous and may pass through 5 – 13 instars before becoming adults. Multiple eggs are encased in an ootheca, an egg case. Depending on the species, the ootheca may be dropped immediately after formation, carried on the end of the female's abdomen, or carried internally in a brood pouch until the immatures are ready to emerge.
Cockroaches are not a specific vector of any disease, but those associated with humans can contaminate food, have an unpleasant odor, and are generally annoying. Cockroaches not associated with humans may live in leaf litter, sand, tree tops, ant nests, etc.
There are 5 families and ~67 species of Blattodea in North American North of Mexico. Helfer (1987) and Triplehorn and Johnson (2005) are good references for information about this order. More information about Blattodea within the First Detector Entomology Wiki can be found here.
Order Isoptera (Termites)
Termites are eusocial insects that live in colonies where there is a division of labor and overlapping generations of older individuals that help raise younger individuals. To the casual observer there may be three "varieties" of termites in a colony, workers, soldiers, and alates. Workers are smaller, 6 – 8 mm long, eyeless, with biting/chewing mouthparts, soft bodied, white to light amber in color, and lack wings. Soldiers are larger, eyeless, have large sclerotized (hardened) amber colored heads and large jaws, a white to light amber colored body, and lack wings. Alates (winged reproductive adults) are larger still, have large compound eyes, a light to dark brown sclerotized (hardened) body, and have two pairs of elongate teardrop shaped wings (these are easily shed and may be lost).
Isoptera are hemimetabolous but can have very complicated life cycles due to the nature of their caste system. During an emergence event a swarm of winged adults leaves the colony. Mated pairs will seek a suitable location to start a new colony and upon finding it they will break their wings off. Some species of Isoptera live within the wood they eat. However, other species require contact with the soil where the colony lives, and will build protective earthen tubes from the colony to the food source.
Termites generally eat dead wood or other dead plant material. Termites are both detrimental and beneficial to human endeavors. Worldwide, termites damage many human structures and produce a significant amount of atmospheric methane (a greenhouse gas). But, the actions of termites enrich the soil by quickly making nutrients stored in dead plant material available to living plants.
There are 4 families and ~44 species of Isoptera in North American North of Mexico. Helfer (1987) and Triplehorn and Johnson (2005) are good references for information about this order. More information about Isoptera within the First Detector Entomology Wiki can be found here.
Order Phasmatodea (Walking Sticks)
Walking sticks are elongate (up to 15 – 180 mm in the U.S.), non-jumping orthopteroids that tend to resemble sticks and twigs. Only one species in the U.S., in southern Florida, has wings. The longest insect in North America is the walking stick Megaphasma denticrus, which can grow to 180 mm long. It ranges throughout the eastern and southern U.S. but is generally not encountered because much of its life is spent in the tops of trees. Walking sticks are herbivores and generally eat tree leaves or grasses. Some species of walking sticks are parthenogenetic, reproducing without males. Walking sticks have a reduced ovipositor and do not produce an ootheca, but instead scatter individual eggs on the ground. Eggs may not hatch until the second year after they are laid.
Walking sticks cannot bite or sting humans. Striped walking sticks (family Pseudophasmatidae) will produce a noxious, irritating milky substance on their backs when molested. At high densities walking sticks may become pests of trees or cultivated plants. Generally this is not the case.
There are 4 families and ~33 species of Phasmatodea in North American North of Mexico. Helfer (1987) and Triplehorn and Johnson (2005) are good references for information about this order.
Order Grylloblattodea (Ice Crawlers)
Ice Crawers are small (15- 30 mm), wingless, soft bodied, non-jumping orthopteroids that were first discovered in 1914. They generally live at high altitudes on talus slopes or in ice caves in Japan, Korea, Siberia, China, and in the northwestern U.S. and Canada. They are nocturnal scavengers that feed on dead insects and other organic matter that get blown onto snow fields. They are so well adapted to the cold you could almost keep one as a pet in your refrigerator. Ice Crawlers are hemimetabolous insects with biting/chewing mouthparts. There is 1 family and ~10 species of Grylloblattodea in North American North of Mexico. Helfer (1987) and Triplehorn and Johnson (2005) are good references for information about this order.
Mantophasmatodea (African Rock Crawlers, Heelwalkers)
These predatory insects were first recognized as a distinct order in 2002. They superficially resemble short fat, soft bodied walking sticks, but have a head and raptorial forelimbs similar to a praying mantid. Amazingly the middle legs are also raptorial. African Rock Crawlers are hemimetabolous insects with biting/chewing mouthparts.
The story of their discovery is very interesting. Initially several fossil specimens were discovered in 40 – 50 million year old amber. Then someone found a pinned specimen in a museum! Luckily the specimens had proper label information. Imagine how terrible it would have been to have discovered evidence of a living fossil, but not know where it had been collected. African Rock Crawlers are only known from Namibia, Tanzania, and South Africa. More than 20 species have been described. Triplehorn and Johnson (2005) is a good reference for information about this order.
6. "Plecopterida" Insects
The "Plecopterida" are a group of 4 insect orders (see below) that share numerous internal and external morphological characteristics. Most have a forward facing (prognathous) head, elongate dorsoventrally flattened body with the thorax almost as long as the abdomen, lost or highly reduced ovipositor (structure used for egg laying), and most are detritivores (some predatory). All members have biting/chewing mouthparts and a hemimetabolous life cycle.
| Order Name | Common Name |
|---|---|
| Plecoptera | Stoneflies |
| Dermaptera | Earwigs |
| Embiidina | Webspinners |
| Zoraptera | Zorapterans |
Order Plecoptera (Stoneflies)
The Plecoptera have been called the insect order most threatened by human activity (Hynes 1993,[13]) because immatures of many species require non-polluted running water to complete their life cycle. Stoneflies are often used as biological indicator species to monitor water quality in streams.
Plecoptera are medium sized (6 – 55 mm), relatively soft bodied, flattened insects. Most have two pairs of membranous wings, although some are wingless. Stoneflies are hemimetabolous with aquatic immatures that are scrapers, detritivores, or predators. Adults have biting/chewing mouthparts although most do not eat or eat very little in the adult form. Males attract mates by drumming their abdomen on a substrate, females drum in return. Stoneflies are generally found near and around the body of water they inhabit as immatures. Some stoneflies, especially the family Capniidae, emerge as adults in the winter and can be found walking on snow.
There are 9 families and ~622 species of Plecoptera in North American North of Mexico. Merritt et al. (2008) and Stewart and Stark (2002)[14] are very important references for information about this order.
Order Dermaptera (Earwigs)
Earwigs are elongate (12 – 30 mm), flattened insects that can be easily recognized by the enlarged forceps-like cerci at the end of their abdomen. These cerci are actually used in defense and, for some species, prey capture. Larger earwigs will use their cerci to pinch when captured. Earwigs have two pairs of wings, or may be wingless. If winged, the first pair is short and leathery and are usually called tegmina. Earwigs are hemimetabolous with biting/chewing mouthparts and most live within rotting vegetation, under bark, and in debris. Most are detritivores, but some will feed on living plants and others are predatory. Earwigs overwinter as adults. They will not burrow into your ear and eat your brain.
There are 6 families and ~23 species of Dermaptera in North America North of Mexico. Amazingly, 12 of those species have been introduced from Europe! Helfer (1987) and Triplehorn and Johnson (2005) are good references for information about this order.
Order Embiidina (Webspinners)
Webspinners are elongate (~11 mm), cylindrical insects with an enlarged pro-tarsal segment that contains silk glands. Embiidina live beneath silk galleries they construct in leaf litter, over the crevices of bark, and among the cracks of rocks. Silk galleries provide protection against predators and parasites. They eat the dead plant material that makes up most of their dwelling. Most individuals live in colonies made of an adult female and her offspring. Only males have wings (two pair), although not all species have winged males. Embiidina are hemimetabolous and have biting/chewing mouthparts. Webspinners are mostly tropical and our species are confined to the southeast and southwest, with one species that reaches to southern Oregon. There are 3 families and ~11 species (3 introduced) in North American North of Mexico. Triplehorn and Johnson (2005) is a good reference for information about this order.
Order Zoraptera
Zoraptera, which means "pure wingless" (which is incorrect because there are winged forms), were first described in 1913. Zoraptera come in two forms, one is white, blind, and wingless, the other is brown (sclerotized), eyed, and has two pairs of membranous wings. Both are about 3 mm long. The wingless form superficially resembles termites, but has a narrower body and runs faster. Individuals are loosely gregarious. Zorapterans apparently feed on fungal spores but may also eat dead arthropods. Zoraptera are hemimetabolous and have biting/chewing mouthparts. There is 1 family and 3 species (one in Hawaii) of Zoraptera in North America North of Mexico. Triplehorn and Johnson (2005) is a good reference for information about this order.
Insect Orders Continued (Groups 7 – 8)
Our overview of the insect orders is continued here.
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Print References
- ↑ Triplehorn, C. A., and N. F. Johnson (eds). 2005. Borror and Delong’s introduction to the study of insects. 7th Edition. Brooks/Cole Publishing, Kentucky, U.S.A. 868 pp.
- ↑ Grimaldi, D. and M. S. Engel. 2005. Evolution of the Insects. Cambridge University Press, New York. 755 pp.
- ↑ Dindal, D. L. (ed). 1990. Soil Biology Guide. John Wiley & Sons, New York. 1349 pp.
- ↑ Merritt, R. W., M. B. Berg, and K. W. Cummins. 2008. An Introduction to the Aquatic Insects of North America. Kendall Hunt Publishing, Dubuque, IA. 1214 pp.
- ↑ Dunkle, S. W. 2000. Dragonflies through binoculars: a field guide to dragonflies of North America. Oxford University Press, New York. 266 pp.
- ↑ Corbet, P. S. 1999. Dragonflies: behavior and ecology of Odonata. Comstock Publishing Associates, New York. 829 pp.
- ↑ Merritt, R. W., M. B. Berg, and K. W. Cummins. 2008. An Introduction to the Aquatic Insects of North America. Kendall Hunt Publishing, Dubuque, IA. 1214 pp.
- ↑ Needham, J. G., M. J. Westfall Jr., and M. L. May. 2000. Dragonflies of North America. Revised edition. Scientific Publishers, Gainesville, FL. 939 pp.
- ↑ Tillyard, R. J. 1917. The biology of dragonflies (Odonata or Paraneuroptera). Cambridge University Press, London. 396 pp.
- ↑ Westfall, M. J. and M. L. May. 1996. Damselflies of North America. Scientific Publishers, Gainesville, FL. 649 pp.
- ↑ Capinera, J. L., R. D. Scott, and T. J. Walker. 2004. Field guide to grasshoppers, katydids, and crickets of the United States. Cornell University Press, Ithaca, NY. 249 pp.
- ↑ Helfer, J. R. 1987. How to know the grasshoppers, crickets, cockroaches, and their allies. Dover Publications, New York, NY. 363 pp.
- ↑ Hynes, H. B. N. 1993. A key to the adults and nymphs of the British stoneflies (Plecoptera), with notes on their ecology and distribution. Third Edition. Freshwater Biological Association, Ambleside, U.K. 92 pp.
- ↑ Stewart, K. W. and B. P. Stark. 2002. Nymphs of North American stonefly genera (Plecoptera). 2nd edition. The Caddis Press. Columbus, Ohio. 510 pp.
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