Anatomy of Madagascar Hissing Cockroaches

The March 2012 study “The Madagascar Hissing Cockroach: A New Model for Learning Insect Anatomy” by William Heyborne, Maggie Fast and Danny Goodding was published in “The American Biology Teacher”.

BODY

Antennae

Function #1. Get information. Cockroaches rely on their antennae to feed them information about:

1. Movement
2. Air pressure
3. Vibration
4. Smells
5. Temperature

Function #2. Finding Food. The antenna contain special cells known as the olfactory receptors. These can bind to the free-floating molecules in the air or on surfaces. By twitching its antennae back and forth, a cockroach can collect food particles. These, of course, are not enough to feed a cockroach, but they can tell it where to find food. A cockroach can tell it is close to food because the smell will grow stronger.

Function #3. Mating. A cockroach uses its antennae to tell when a mate is ready to breed, which is done through pheromones. This smell is nearly undetectable to humans but signals to other cockroaches that it’s time to breed. For males, they’ll release a pheromone that is even capable of enticing a female to breed. The antennae also help cockroaches distinguish males from females. Laboratory experiments have shown that, without antennae, cockroaches struggle or fail to breed.

Function #4. Navigating. Roaches aren’t blind, but they can’t see clearly at a distance. At close range, they have night vision and an almost 360-degree view. However, if they relied on sight alone, they may fail to see obstacles in their path until it’s too late. To compensate, antennae work as a second set of more eyes that enable them to navigate the world.

Function #5. Avoiding Predators. Cockroaches use their antennae as an early warning system. They can not only smell the unique scent of the predator but use the change in air pressure to tell which direction it’s coming from. That’s paired with detecting vibrations.

Function #6. Detecting Weather. This is accomplished with thermoreceptors, which are special cells designed to sense the temperature of the air. It even helps the antennae detect how much water vapor is present in the surroundings.

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Notum

The notum is the dorsal portion of an insect’s thoracic segment.

Pronotum

Pronotum (prothorax) is a prominent plate-like structure that covers all or part of the thorax of some insects. The pronotum covers the dorsal surface of the thorax.

Pronotum can easily determine the sex of a cockroach. Both male and female Madagascar hissing cockroaches possess bumps on the prothorax. The male’s bumps are much more conspicuous than the female’s.

Bumps on Prothorax

Thorax

Besides the pronotum, Notum has mesothorax (mesonotum) and metathorax (mesonotum).

Mosothorax

aka Mesonotum. Second thoracic segment.

Metathorax

aka Metanotum. Third thoracic segment.

Abdomen

Sclerite

Sclerites — the chitinous plates constituting the hard surface of an insect. They usually do not correspond to particular anatomical areas (particular segments of the thorax or abdomen, for instance).

Spiracles

If you look along the edges of the dorsal surface of a hissing cockroach’s abdomen, you will notice a pair of tiny, dark circles on each segment. If you were to look at these darkened areas under a microscope, you would see tiny openings in the insect’s exoskeleton, or hardened body surface. These openings are the spiracles.

It is through these openings that air enters and exits the insect’s body. Rather than having a nose with only one pair of nostrils, insects have many pairs of spiracles along their body surface. When the hissing cockroach quickly forces air out of these spiracles, it creates a hissing sound.

Different Types Of Spiracles

The hissing roach’s respiratory system is also unique in another way. This species possesses two types of spiracles:

• Abdominal spiracles
• Thoracic spiracles

Their abdominal spiracles are located on the outside of the body, where the air escapes. The thoracic spiracles can be found within the cockroach and connect the inner thoracic cavity to the abdominal spiracles. This is how air storage is linked to the external world.

However, the hissing roach has no metathoracic spiracles. These are present in many other insects. In exchange, they have more abdominal spiracles, which may be linked to their ability to hiss.

In fact, hissing roaches may be the only known insect species that can generate such a sound in this manner. Other insects that produce a sound do so by vibrating or rubbing their body parts together.

See full article here

Cerci

Cerci (singular cercus) are paired appendages on the rear-most segments of many arthropods, including insects and symphylans. In groups such as crickets and cockroaches, cerci play important sensory roles. They have been shown to be sensitive to puffs of air and low-frequency vibration, and thus trigger anti-predatory responses such as escape in response to certain predators.

Entomologists who have investigated this have found that cockroaches detect the puff of wind generated by a nearby moving object. They run away from the wind. And it has to be a puff of wind, not a steady breeze. To make the roach run, the wind speed has to increase sharply over a small fraction of a second. When these hairs are struck by a puff of air, they cause nerve impulses to be sent to the insect’s leg muscles. A cockroach with one circus damaged or removed makes wrong turns. A roach with both cerci damaged or removed doesn’t try to escape at all.

See full article here

HEAD

Head anatomy of Madagascar hissing cockroach

Source: Study “The Madagascar Hissing Cockroach: A New Model for Learning Insect Anatomy” (William Heyborne, Maggie Fast and Danny Goodding).

LEGS

Legs have three pair (6 legs).

Cockroach leg

Trochantin

aka the trochantin, trochantine or trochantinus. Trochantin — the small, somewhat triangular-shaped sclerite articulating with the coxa.

Coxa

The coxa is the stout, flat, proximal piece of each leg.

Trochanter

aka Subapical seta. The trochanter is a very small piece attached to the distal end of the coxa.

Femur

The thigh, like the arm, contains a single bone, the femur. The femur resembles the coxa in form, but is more slender.

Tibia

Tibia is slender, but the longest podomere of the leg in cockroach. Tibia surface has articulated spines (tibial spurs).

Tarsomeres

aka Tarsus / Tarsi / tarsal segments. Tarsus made up of five sub-segments piece of chitin.

Tarsomeres/Tarsus of a cockroach (highlighted)

Photo from study “Foot Morphology and Substrate Adhesion in the Madagascan Hissing Cockroach, Gromphadorhina portentosa”.

Tarsus

The tarsus of an insect’s leg is made up of five segments and functions much like an ankle. It connects to the pretarsus which functions like a foot.

Cockroach Tarsus and Pretarsus

Photo from study “Morphology and ultrastructure of the tarsal adhesive organs of the madagascar hissing cockroach gromphadorhina portentosa”.

Tarsal pads

aka Aroliar/pretarsal pads, aka Euplantulae

Photo from study “Effects of aging on behavior and leg kinematics during locomotion in two species of cockroach”

The pretarsal pads and lobes have adhesive setae (tenent hairs) that allow the insect to climb and hold onto smooth surfaces. Tactile setae present on each segment of legs. The stiffness of tarsal pads has been found to be affected by the insects’ age. The pads of aged cockroaches were found to be less flexible than those of younger ones, concurrent with a reduced climbing performance.

Pretarsus

aka Acropod, aka posttarsus. Pretarsus arises from the distal end of the eutarsus. Pretarsus has two structure: Arolium and Claws.

Arolium

Most insects are capable of adhesion to smooth surfaces like glass. On the tips of their legs ants and other insects have a specialized appendage called a tarsus. The tarsus includes claws for locomotion on rough terrain, as well as a flexible pad, called an arolium, for adhesion to smooth surfaces. The surface of the arloium varies within the insects: In flies and beetles it is covered with fine hairs, while on ants, bees, roaches, and grasshoppers it is a flat flexible cuticle. The arolium is coated with viscous secreted fluids allowing it to work like a wet suction cup.

Claws

aka Unguis, aka Hooks. One pair Tarsal/Pretasus/Pretarsal claws.

The claws are the final (furthest from the body) segment in the leg of an insect. Move on the smooth surface by the help of arolium and on the rough surface with the help of claws.

Cockroach Pretarsus — Arolium and Claws

INTERNAL ANATOMY

Source: Study “The Madagascar Hissing Cockroach: A New Model for Learning Insect Anatomy” (William Heyborne, Maggie Fast and Danny Goodding).

FAQ

My cockroach has no part of its legs. Why?

There are two reasons for this — improper care and a bad diet. Be careful not to jerk the insect, since the feet have sticky paws and looks that grip tightly. If you pull to hard, you may injure the insect.

The diet should be varied. Cockroaches should get enough protein. Otherwise, they will eat their own Pretarsus and even the entire Tarsus. Ideally, cockroaches should always have access to water and dry food containing protein (dog/cat/fish food). Every 2–3 days, you can give various fruits or vegetables (apples, carrots, etc.).

What if a cockroach loses one of an antennae?

Losing even one antenna can compromise a cockroach. It will be:

1. Disoriented
2. Easily lost
3. Prone to running into objects
4. Vulnerable to predators
5. Unable to find food
6. Unable to mate

In laboratory settings, cockroaches with their antennae removed were observed to have a dramatic behavioral change. They became more physically aggressive and rammed themselves into surfaces and items.

Can Cockroaches Regrow Antennae?

Since cockroaches have an impressive regeneration ability, antennae will grow back. Depending on its age, a cockroach can regrow up to 30% of its lost antennae during the next molt. It may take several molts to regenerate the lost appendage completely. Once it does, however, it will regain complete use of the antennae and return to normal.

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See also

• List of species of genus Gromphadorhina
• Madagascar Hissing Cockroach: Common Info
• How do Madagascar Cockroaches Make a Hissing Sound
• Health problems of Madagascar Hissing Cockroaches
• How to Determine the Sex of Madagascar Hissing Cockroaches
• How to Set Up a Tank for Madagascar Hissing Cockroaches
• How to Provide Proper Temperature for Hissing Cockroaches
• How to Provide Proper Humidity for Hissing Cockroaches
• List of Foods for Madagascar Hissing Cockroaches
• How do Madagascar Hissing Cockroaches Fight
• How to Breed Madagascar Hissing Cockroaches
• How do Madagascar Hissing Cockroaches Molt
• Body Types Of Madagascar Hissing Cockroaches
• Mites on Madagascar Hissing Cockroaches

References

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6. Claw — entomologists’ glossary. (n.d.). Amateur Entomologists’ Society. https://www.amentsoc.org/insects/glossary/terms/claw/
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14. Ridgel, A. L., Ritzmann, R. E., & Schaefer, P. L. (2003). Effects of aging on behavior and leg kinematics during locomotion in two species of cockroach. Journal of Experimental Biology, 206(24), 4453–4465. https://doi.org/10.1242/jeb.00714
15. Schmitt, C., & Betz, O. (2017). Morphology and ultrastructure of the tarsal adhesive organs of the madagascar hissing cockroach gromphadorhina portentosa. ResearchGate. https://www.researchgate.net/publication/319078922_Morphology_and_ultrastructure_of_the_tarsal_adhesive_organs_of_the_Madagascar_hissing_cockroach_Gromphadorhina_portentosa
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21. Wikipedia contributors. (2022, January 10). Cercus. Wikipedia. https://en.wikipedia.org/wiki/Cercus

Last update: April 18, 2022