Sinea diademaspined assassin bug

Geographic Range

Sinea diadema is typically found in Southern North America, namely in the Southern United States and Northern Mexico. (Arnett, 1993)


Sinea diadema is generally found in grasslands, gardens, and fields. They are found living among flowers and in crops. ()

Physical Description

Sinea diadema has a long, narrow head that supports a short beak, formed by three segments. Also found on the head are slender antennae, each composed of four segments. The large size of the head is to support the beak that is so necessary for prey capture and consumption. Unlike other assassin bugs that are often bicolored, Sinea diadema is dark brown or a dull red. The eyes are reddish brown. The front legs are slightly swollen and covered with spines. The abdominal area is expanded, flat, and displays a pale spot on the rear margin of every segment. Because the middle of the abdomen is so wide, the wings cannot completely cover the entire body. (Lyon, 2002; Mahr, 1996)

  • Sexual Dimorphism
  • sexes alike
  • Range length
    12 to 16 mm
    0.47 to 0.63 in


After hatching from the egg, Sinea diadema develops into a nymph, resembling the adult form, but without wings. The nymph molts five times, and will hibernate just before the last molt to emerge in the summer season as a reproductive adult. (Mahr, 1996; Texas Cooperative Extension, 1999)


Although both vision and antennal olfaction are important to various life processes, no further information was available for specific mating systems of Sinea diadema.

The female Sinea diadema deposits large amounts of brown, cylindrical eggs in an upright position. These eggs are usually located on a leaf or within the soil, and are covered with a reddish brown secretion. (Arnett, 1993)

  • Breeding season
    June though October
  • Average eggs per season

After laying the eggs, the female and male have no further parental contact with the young.

  • Parental Investment
  • no parental involvement


Antennal olfaction plays a large role in the finding of a habitat. Not only is this sensory input important for the habitat location, it is also important for locating areas of prey and individual prey organisms. Studies have shown that in some cases, olfaction is more important than vision for locating habitats. (Freund and Olmstead, 2000a; Freund and Olmstead, 2000b)

Communication and Perception

Antennal olfactions and vision are key to the lifestyle of Sinea diadema. The ability to sense vibrations is also important, especially when it comes to enemy avoidance. However, studies have shown that vision is the most important sense for avoiding enemies. (Freund and Olmstead, 2000a; Freund and Olmstead, 2000b; Taylor and Schmidt, 1996)

Food Habits

Sinea diadema preys on organism such as aphids, caterpillar eggs, leafhoppers, lady bugs, and asparagus beetle eggs and larvae. The sharp beak mouthpart on the head is used to stab into the prey, allowing Sinea diadema to pierce through the prey's outer covering and then to suck out the body fluids. (; Lyon, 2002; Mahr, 1996; Texas Cooperative Extension, 1999)

  • Animal Foods
  • eggs
  • body fluids
  • insects


The dark brown and dark red coloring allows for cryptic coloration. Studies have shown that if Sinea diadema is in a state of starvation, it will resort to cannibalism, namely on the siblings that surround it. (Freund and Olmstead, 2000a)

  • Anti-predator Adaptations
  • cryptic

Ecosystem Roles

Because Sinea diadema feeds on many pest insects that destroy valuable crops, they are a desired species. They contribute to the natural balance of their habitat and control insect populations in the process.

Economic Importance for Humans: Positive

These bugs attack many agricultural and horticultural pests, so are beneficial to human interests. (Lyon, 2002; Mahr, 1996; Texas Cooperative Extension, 1999)

  • Positive Impacts
  • controls pest population

Economic Importance for Humans: Negative

Although these bugs typically avoid humans, if roughly handled, Sinea diadema can bite. The bite may be painful, but not deadly. (Texas Cooperative Extension, 1999)

  • Negative Impacts
  • injures humans
    • bites or stings

Conservation Status

This species is not believed to need any special conservation.


Matthew Wund (editor), University of Michigan-Ann Arbor.

Lance Betway (author), University of Michigan-Ann Arbor, Phil Myers (editor), Museum of Zoology, University of Michigan-Ann Arbor.



living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map


living in landscapes dominated by human agriculture.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.


an animal that mainly eats meat


uses smells or other chemicals to communicate


having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.

  1. active during the day, 2. lasting for one day.

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature


union of egg and spermatozoan


the state that some animals enter during winter in which normal physiological processes are significantly reduced, thus lowering the animal's energy requirements. The act or condition of passing winter in a torpid or resting state, typically involving the abandonment of homoiothermy in mammals.


An animal that eats mainly insects or spiders.

internal fertilization

fertilization takes place within the female's body


A large change in the shape or structure of an animal that happens as the animal grows. In insects, "incomplete metamorphosis" is when young animals are similar to adults and change gradually into the adult form, and "complete metamorphosis" is when there is a profound change between larval and adult forms. Butterflies have complete metamorphosis, grasshoppers have incomplete metamorphosis.


having the capacity to move from one place to another.


reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

scrub forest

scrub forests develop in areas that experience dry seasons.

seasonal breeding

breeding is confined to a particular season


reproduction that includes combining the genetic contribution of two individuals, a male and a female


that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).


Living on the ground.

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.


A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.


movements of a hard surface that are produced by animals as signals to others


uses sight to communicate


University of Kentucky Department of Entomology. 1995. "Assassin Bug" (On-line ). Accessed 03/18/03 at

Arnett, R. 1993. American Insects. Gainesville, Florida: Sandhill Crane Press, Inc..

Freund, R., K. Olmstead. 2000. Role of Vision and Antennal Olfaction in Habitat and Prey Location By Three Predatory Heteropterans. Environmental Entomology, Volune 29/Issue 4: 721-732.

Freund, R., K. Olmstead. 2000. The Roles of Vision and Antennal Olfaction in Enemy Avoidance By Three Predatory Heteropterans. Environmental Entomology, Volume 29/Issue 4: 733-742.

Lyon, W. 2002. "Assassin Bug" (On-line ). Accessed 03/18/03 at

Mahr, S. 1996. "Assassin Bugs" (On-line). Know Your Friends. Accessed March 18, 2003 at

Taylor, J., J. Schmidt. 1996. The Effect of Hunger On Intraspecific Interactions Between First-Instar Sinea diadema . Journal of Insect Behavior, Volume 9/Issue 1: 37-45.

Texas Cooperative Extension, 1999. "Assassin Bug" (On-line). Accessed November 23, 2004 at