Order Hemiptera (True Bugs, Aphids, Scales, and Allies)
Introduction
Recent changes have resulted in the combination of orders Homoptera and Hemiptera into one order called Hemiptera. See Hemiptera Names, right. For over 100 years most entomologists recognized two closely related orders, (A) Hemiptera and Homoptera. Then new evidence based on DNA showed us that these all belonged to the same major group (B), and Homoptera should really be split into three small groups. If you have an older book that recognizes two orders (Hemiptera and Homoptera) then "Hemiptera (true bugs)" are what newer references call "Heteroptera (true bugs)". Also "Homoptera" of older literature is broken into three groups called Sternorrhyncha (stern-o-RHIN-ka) (aphids, whiteflies, scales), Auchenorrhyncha (awe-ken-o-RHIN-ka) (cicadas, hoppers) and Coleorrhyncha (only known from the southern hemisphere). The name Homoptera is no longer used in technical literature.
Hemiptera come in a wide variety of forms, from organisms that are obviously insects, like assassin bugs, to organisms that are so reduced it is difficult to tell they are animals, such as scale insects. The one unifying character is the arrangement of the mouthparts into an elongate beak (see Assassin Bug figure below). At the center of the beak are two stylets (maxillae) that have two groves on their inner surface, so when both stylets are placed together two channels are created. One channel is used to suck food into the body, the other channel is used to pump saliva or venom out of the body. On each side of the maxillae are two more stylets, the mandibles. These can slide back and forth along the beak independently of the inner maxillae to help penetrate the food item. All four stylets are surrounded by a thin sheath composed of the labium. A generalized feeding event would go as follows: the beak is pressed against the food item (plant or animal); at the tip of the beak the mandibular stylets emerge and cut into the food item; then the inner most maxillary stylets begin ejecting saliva (or venom) through the salivary channel as the mandibular stylets continue to cut into the food item and the beak is inserted further; finally, fluid is sucked up through the food channel of the maxillary stylets. The presence of the salivary channel and injection of saliva is the main reason many hemipterans are important vectors of disease.
Life Cycle
Hemiptera are Hemimetabolous, their life cycle consists of three phases: egg, multiple instars, and adult. Simple metamorphosis is a common name for this life cycle. The immatures tend to look like miniature versions of the adults, except in the immature the head is larger in proportion to the body, wings are not fully formed and appear as wing buds, and reproductive structures are not developed. Insect orders with this life cycle are grouped under the term Exopterygota because of visible wing buds on the immatures.
Mature and immature Hemiptera of some plant feeding groups may use the same food source.
How to Photograph Hemiptera
Some Hemiptera are shy and will drop, run, or hop away as you approach. These may need to be captured and cooled/stunned/killed before they can be photographed. Other Hemiptera, such as assassin bugs and certainly scale insects are less likely to move and photography of these groups is easier. If you suspect an insect is feeding on a plant, try to get photos of the plant and any suspected feeding damage caused by the insect.
How to Collect Hemiptera
Generally Hemiptera can be collected using a sweep net. Hemiptera are alert and many are good evaders (jumping, falling, running, etc.) therefore you should not disturb the collection area before you begin collecting. Scale insects and other sedentary Hemiptera can be collected by removal of all or a portion of the leaf or branch to which they are attached.
For short term preservation Hemiptera can be killed in a killing jar or preserved alcohol. Scale insects can be preserved in alcohol or left to dry on the plant they were feeding on (but see below). For long term storage Hemiptera should be pinned and scale insects should be preserved in alcohol and/or cleared and slide mounted. Scale insects that are meant to be slide mounted should not be allowed to dry out.
How Hemiptera Cause Damage
Because of their specialized mouthparts Hemiptera do not bite chunks out of plant leaves, stems, roots, or fruits like caterpillars and grubs. Instead plant feeding Hemiptera pierce plant parts and may leave a distinct pucker or dot. Additionally some vector diseases which create their own distinctive symptoms.
Types of Hemiptera
There are three major suborders of Hemiptera: Heteroptera (True Bugs); Auchenorrhyncha (Cicadas, Hoppers); and Sternorrhyncha (Aphids, Whiteflies, Scales).
Suborder Heteroptera (True Bugs)
The Heteroptera are small to very large (0.5 – 65 mm) insects with piercing-sucking mouthparts that arise from the front of the head, scent glands (reduced in aquatic forms but well developed in plant feeding species, e.g. "stink bugs"), and unique front wings with a hardened corium in the anterior portion of the wing with the rest of the wing membranous. Heteroptera have simple metamorphosis (hemimetabolous).
Several groups of Heteroptera are aquatic and semi-aquatic, including backswimmers, water boatmen, water striders (different from water sPiders), and giant water bugs. Some water striders in the genus Halobates live on the open ocean. Giant water bugs occasionally fly to lights are night or are found in lighted swimming pools. They can also be pests at fish hatcheries where they prey on fry.
Bed Bug
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The famous bed bug (Cimex lectularius) is found in this sub-order. It is small, round, and wingless, but visible to the naked eye. It may be bright red after taking a meal. Bed bugs lay eggs in cracks and crevices. Eggs hatch in 6-10 days and immatures look similar to adults. Bed bugs go through five instars and may complete three or four generations in a year. Adult bed bugs can live for several months without feeding if conditions are favorable. Bed bug infestations can be recognized by blood stain smears on walls and bedding. Bed bugs are a nuisance but thankfully do not transmit disease. If you suspect you have found a bed bug, keep the specimen so it can be identified. Preserve the specimens in alcohol (80% ethyl alcohol is best, but rubbing alcohol will do). Try to collect as many specimens as you can to ensure you have an identifiable adult. Take the specimens to the appropriate specialist to be properly identified. Not all bugs in this family are bed bugs. Some feed on bats or birds, and may infest homes occupied by these primary hosts, so correct identification is essential even if bed bug is strongly suspected. See Mallis (1997)[1] for more information. |
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The assassin bugs (family Reduviidae) are predatory and generally viewed as beneficial in crops and gardens. Heteroptera associated with plants as pests or occasional nuisances include plant bugs (family Miridae), chinch bug (Blissus leucopterus, family Blissidae), cotton stainers (family Pyrrhocoridae), leaf-footed bugs (family Coreidae), and stink bugs (family Pentatomidae).
Suborder Auchenorrhyncha (Cicadas, Hoppers)
The Auchenorrhyncha have piercing-sucking mouthparts that arise from the back of the underside of the head, three segmented tarsi, and short bristle-like antennae.
The cicadas (family Cicadidae) are medium to large (10 – 50 mm) insects with membranous wings. There are over 150 cicada species known from the United States and males of each species make a characteristic mating call. In some species the life cycle is 17 years long and a mass emergence takes place on the 17th year. A closely related group of species has 13 year cycles. The mating songs of these emergences can be deafening in good habitat. Adult females insert their eggs in the fine tips of branches (which can damage nursery stock). After the egg hatches the immature drops to the ground, burrows to the roots of a perennial plant (typically a tree), and feeds on the roots. Many years later (4 to 17 depending on the species) it emerges, molts, becomes an adult, and reproduces. Adults only live for about a month.
The "hoppers" are represented by many different families. Treehoppers (family Membracidae) are known for the large pronotum that covers the head and extends beyond the abdomen. The froghoppers or spittlebugs (family Cercopidae), are well known for the white frothy spit-like mass the immature produces and lives within while feeding on a host plant. The leafhoppers (family Cicadellidae) comprise a large group of about 2500 species in North America. While most leafhoppers are only found in specific parts of the country on specific plants, many economically important species cause damage by directly impacting the plant or by vectoring pathogens. Many other "hopper" families contain members that feed on vines, trees, grasses, and can even be found under loose bark, but thankfully few of these are of economic importance.
Potato Leafhopper
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The potato leafhopper (Empoasca fabae (Harris)) is an important pest of alfalfa, but is also found on potatoes, peanuts, soybeans, and other vegetables. Adults are about 3 mm long, pale green, and hop when disturbed. Immatures move across leaves in a sideways manner when disturbed. They look similar to adults but lack fully formed wings. The potato leafhopper overwinters in the Gulf States and migrates north each spring. There are several generations per year. |
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Suborder Sternorrhyncha (Aphids, Whiteflies, Scales)
The Sternorrhyncha have piercing-sucking mouthparts that appear to arise from between the front legs, one or two segmented tarsi, and antennae (when present) that are long and filiform. Scale insects, represented by numerous families within the Sternorrhyncha, may lack wings, antennae, and even legs. They are generally sedentary and clothed in a waxy covering that can be diagnostic to family.
The jumping plant lice (family Psyllidae), whiteflies (family Aleyrodidae), and aphids (family Aphididae) generally have winged members and are recognizable as insects. Aphids can be distinguished from other similar insects by the cornicles, two tube like structures that arise from the dorsal portion of the abdomen. The aphid life cycle can be complicated and includes winged and wingless individuals, sexual and asexual reproduction, production of one sex or another, and host shifts. Some aphids secrete chemicals that cause plants to produce galls within which the aphids feed and develop.
Strawberry Aphid
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The strawberry aphid (Chaetosiphon fragaefolii (Cockerell)) is 0.9 – 1.8 mm in length, with elongate oval pale green bodies and reddish eyes (see figure, right). These cause little direct damage to strawberries but are important vectors of disease. They are most numerous on the underside of young leaves. Strawberry aphids breed parthenogenetically throughout the summer, producing winged females in the fall and early winter. |
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The "scale insects" are a group composed of about 16 families. The females are sedentary and do not move. Mature males are mobile and generally have one pair of wings similar to a true fly, but lack mouthparts. The first instar has legs and will crawl away from its mother before settling down to feed. When scale insects become too numerous they can injure and even kill a plant by extracting large quantities of sap and nutrients. The products of some scale insects are used by humans including, edible dried honeydew, waxes that can be used as chewing gum, wax suitable for candle making, crimson dye, and shellac, which is produced by lac scales (family Kerridae).
Cottony Cushion Scale
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The cottony cushion scale (Icerya purchasi Maskell) is easily recognized by the white cottony egg masses which can be up to 12 mm in length (see figure, right). Each egg mass can contain up to 1000 bright red eggs. After hatching, immatures begin feeding and become covered in a white cottony wax. The cottony cushion scale is a pest of citrus, but can also infest a variety of fruit and shade trees. Large scale outbreaks of this imported pest occurred in California and elsewhere historically. But after introduction of the vedalia ladybeetle (Rodolia cardinalis (Mulsant)) it was reduced to an occasional pest of minor importance. |
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Summary and References
There are 42 families and ~568 species of Heteroptera in North American North of Mexico. Slater and Baranowski (1978)[2] is an excellent, but hard to find resource and Triplehorn and Johnson (2005)[3] is a good general reference for information about this suborder.
There are 38 families and ~759 species of Auchenorrhyncha and Sternorrhyncha in North American North of Mexico. Triplehorn and Johnson (2005) is a good general reference for information about this suborder.
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Print References
- ↑ Mallis, A. (ed.). 1997. Handbook of pest control: the behavior, life history, and control of household pests. 8th ed. Mallis Handbook & Technical Training CO. Cleveland, OH. 1456 p.
- ↑ Slater, J.A. and R. M. Baranowski. 1978. How to know the true bugs (Hemiptera – Heteroptera). The Pictured Key Nature Series. Wm. C. Brown Co., Dubuque, IA, 256 pp.
- ↑ 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.
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