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Sinea diademaspined assassin bug

By Lance Betway

Ge­o­graphic Range

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

Habi­tat

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

De­vel­op­ment

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)

Re­pro­duc­tion

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
    Many

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

  • Parental Investment
  • no parental involvement

Be­hav­ior

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

Pre­da­tion

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.

Con­trib­u­tors

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.

Glossary

Nearctic

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

agricultural

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.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

cryptic

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.

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

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

fertilization

union of egg and spermatozoan

hibernation

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.

insectivore

An animal that eats mainly insects or spiders.

internal fertilization

fertilization takes place within the female's body

metamorphosis

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.

motile

having the capacity to move from one place to another.

oviparous

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

sexual

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

temperate

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).

terrestrial

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.

savanna

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.

vibrations

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

visual

uses sight to communicate

Ref­er­ences

Uni­ver­sity of Ken­tucky De­part­ment of En­to­mol­ogy. 1995. "As­sas­sin Bug" (On-line ). Ac­cessed 03/18/03 at http://​www.​uky.​edu/​Agriculture/​Entomology/​ythfacts/​mystery/​mystry1.​htm.

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 http://​ohioline.​osu.​edu/​hyg-fact/​2000/​2082.​html.

Mahr, S. 1996. "As­sas­sin Bugs" (On-line). Know Your Friends. Ac­cessed March 18, 2003 at http://​www.​entomology.​wisc.​edu/​mbcn/​kyf305.​html.

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 http://​insects.​tamu.​edu/​fieldguide/​aimg51.​html.

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