Illinois Natural History Survey - University of Illinois

Flatbugs (Insecta: Heteroptera: Aradidae)


Aradus cincticornis
Photo by Steve Taylor

The flatbugs comprise an obscure little family of insects in the order Heteroptera (the "True Bugs"). In the temperate zone, these animals are often found under loose bark of dead trees. Their coloration, often mottled browns/blacks/grays/yellows, makes them quite difficult to detect. Their cryptic nature should be apparent in some of these images where it is difficult to make out where the bark ends and the animal begins!


Photo by Steve Taylor

In the midwestern United States, the best way to find these animals is to find an area with large tracts of mature forest (a feat becoming increasingly difficult throughout the world), and then look for trees that have died naturally and have had several years to 'mature'.


Photo by Steve Taylor

In such areas, if you are lucky, you may find a dead tree or large limb (such as that above) with a healthy growth of fungus (here, the genus Stereum, or 'False Turkey's Tail Fungus'). This is an excellent place to look for members of the genusMezira.


Photo by Steve Taylor

The animals above are members of the genus Mezira. Pictured are both the male and female of the adult stage (the largest and darkest individuals), the second through fifth nymphal stages, and a rather poor view of an egg (the light colored object near the center of the picture) with a first instar nymph emerging from it.


Photo by Steve Taylor

The genus Neuroctenus, above (ruler marks are millimeters), looks very similar to Mezira, but is usually found in somewhat drier environments. There is also a group of eggs. Eggs are almost always found in groups, and are deposited in such a way as to be aligned with the grain of the wood.


Photo by Steve Taylor

Above is a picture of a third instar nymph of another species, Aradus acutus, which is fairly common in the midwest in appropriate habitat.


A nymph of an Australian aradid, photo by and courtesy of Dave Britton.


An adult male of an Australian aradid - this morphology is generally typical of tropical leaf litter inhabiting species, photo by and courtesy of Dave Britton.


This aradid (above), Dysodius lunatus, lives on the outside of the bark of trees in the American tropics. It is fairly large and more apparent than most aradids (in spite of it's cryptic markings), and is thus commonly encountered in major insect collections. Courtesy of and Photo by Dexter Sear, IO Vision.


  (c) Rune Axelsson Lenhard, Gerald. Louisiana State University. Image 0013002. April 27, 2002.
In Europe, the Pine Bark Bug, Aradus cinnimomeus (female, to left, above), is a sometimes serious pest of pines, and is unusual in that it feeds on living trees. In North America, two other species, Aradus kormilevi (a female shown, to right, above) and Aradus antennalis occur, and they occupy a similar niche. These bugs are often brachypterous as adults (having short, nonfunctional wings) or, especially in males, stenopterous (having narrow, straplike wings).



In 1920, C. S. Spooner published a note on the mouthparts of the Aradidae. He had discovered that the flatbugs are unusual in that the stylets are coiled up inside of the head of the animal, instead of being basically straight (the case in almost all of the rest of the Heteroptera and Homoptera). Interestingly, the direction and manner in which they are coiled is of some significance in the classification of the subfamilies of the Aradidae.

Spooner held a position at Eastern Illinois University (Charleston, Illinois) for some time, and the insect collection there is named in his honor. The image above, a side view of a head cross-section, comes from a 1930 German publication by H. Weber.


Photo by Steve Taylor

While working on my masters degree, I noticed that in some batches of eggs there were a few eggs that were almost black in color. It turns out that these eggs have been parasitized by a very small wasp. The two red arrows in the above image point to a 'normal' egg (upper arrow) which is creamy white with a 'normal' slit where the first instar nymph has emerged from the egg, and a parasitized egg (lower arrow) with a roundish hole where a parasitic wasp has emerged.


Photo by Steve Taylor

The wasp above emerged from the parasitized eggs. It is less than 2 millimeters in length, and is a member of the family Scelionidae, which contains a number of species that parasitize the eggs of heteropterans.

There are few good sources of information on the family Aradidae. Three key works are given below:

Froeschner, R. C.. 1988. Family Aradidae Spinola, 1837, pp. 29-46. In T. J. Henry and R. C. Froeschner (eds.). Catalog of the Heteroptera or True Bugs, of Canada and the Continental United States. E. J. Brill, Leiden. 958 pp.

Kormilev, N. A. and R. C. Froeschner. 1987. Flat Bugs of the World. A synonymic List (Heteroptera: Aradidae). Entomography 5: 1-246.

Usinger, R. L. and R. Matsuda. 1959. Classification of the Aradidae (Hemiptera-Heteroptera). British Museum (Natural History), London. 410 pages.



Aneurus sp. from West Virginia.
Photo by and courtesy of Stephen Cresswell



Neuroctenus sp. (adult female) from West Virginia.
Photo by and courtesy of Stephen Cresswell


I am an author on several shorter papers on Aradidae (below), and am still involved in some research on this odd group of insects.

Leschen, R. A. B. and S. J. Taylor. 1987. Notes on the biology and distribution of Aradus robustus Uhler (Hemiptera: Aradidae). Entomological News 98(4):183-185.

Nardi, J., C. M. Bee, L. A. Miller, and S. J. Taylor. 2009. Distinctive features of the alimentary canal of a fungus-feeding Hemipteran, Mezira granulata (Heteroptera: Aradidae). Arthropod Structure & Development 38:206-215.

Taylor, S. J. 1985. Notes on the biology and ecology of Aradidae. Informal conference on the Ecology of the Heteroptera, annual meeting of the Entomological Society of America, Hollywood, Florida.

Taylor, S. J. 1987. Ecology, biology and coexistence of four species of Aradidae from the southeastern United States. M.S. Thesis in Zoology, Department of Biology, Texas A&M University, College Station, Texas. 1987. ix + 102 pp.

Taylor, S. J. 1988. Skototaxis in three species of flatbugs (Heteroptera: Aradidae). Annals of the Entomological Society of America 81(3):537-538.

Taylor, S. J. 1988. Observations on parental care in the family Aradidae (Heteroptera). The Great Lakes Entomologist 21(4):159-161.

Taylor, S. J. and S. A. Gil. 2009. State records and confirmations of Aradidae (Hemiptera: Heteroptera) from Louisiana, U.S.A. The Florida Entomologist 92(2):199-207.

Taylor, S. J. and S. P. Lewis. 1989. Notes on the habitat and distribution of Acaricoris ignotus Harris and Drake (Heteroptera: Aradidae). The Southwestern Naturalist 34(1):154-155.

Taylor, S. J. and J. E. McPherson. 1989. State records and confirmations of Arkansas flat bugs (Heteroptera: Aradidae). The Great Lakes Entomologist 22(1):19-23.

Taylor, S. J. and J. E. McPherson. 1989. Distributional records of some Florida Aradidae (Heteroptera). Florida Entomologist 72(2):265-267.

Davidova-Vilimova, J., S. J. Taylor, and J. E. McPherson. 1996. A new species of Mezira (Heteroptera: Aradidae) from the southeastern United States. Proceedings of the Entomological Society of Washington 98(4):630-639.


Aradus sp., an adult male of a western North American species.
Photo by Ken Gray. Use by permission of Oregon State University.

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