As an insect pet lover, you may be interested in learning the number of cockroaches’ legs with their external anatomy. This article might help you know the accurate answer: how many legs does a cockroach have?
Quick answer of how many legs a cockroach has: a cockroach has six (6) legs that distribute in the prothorax, mesothorax, and metathorax regions of the thorax. These six legs (3 pairs) are well-developed in cockroaches, each with almost six segments.
You will know the details of the appearance and segments of each leg from the cockroach with a labeled diagram. Again, I will share the number, appearance, and segments of the legs from various types of cockroaches at the end of this article.
So, if you want to know – how many legs a hissing or German cockroach has, let’s continue this article till the end.
How many legs does a cockroach have?
A cockroach typically has 3 pairs of jointed legs that are moved by sets of extrinsic and intrinsic muscles. Again, these three pairs of legs (6 legs) are furnished with a range of sensory receptors.
You will also find some of the mechanical structures in each leg of the cockroach, like hair, spine, and adhesive pads.
- So, a cockroach has – six legs or three (3) pairs of legs,
In most insect like a cockroach, the main functions of their legs are to enable walking on land. But, you will find the modification of the legs in cockroaches and also in other insects.
These modified legs of the cockroaches and other insects allow them to use other kinds of locomotion (like jumping, swimming, and walking on water). Again, their legs are specialized for a range of other various tasks, including grasping, grooming, and others.
Though all these six legs of the cockroach are well-developed, the length is different. The length and diameter of the hind pairs of legs (legs in metathorax) are larger in a cockroach.
Again, the middle pair of legs is smaller than the hind pair of legs in a cockroach. The front (anterior) pair of cockroach legs (another name – prothoracic legs) is comparatively shorter than these of the middle and hind pairs.
Let’s see the average length of 3 pairs of cockroach legs from Table 1 –
| 3 pairs of cockroach leg | Synonym | Length |
| Anterior legs | Prothoracic legs | 8.5 – 10 millimeters |
| Middle legs | Mesothoracic legs | 7.5 – 8.5 millimeters |
| Hind legs | Metathoracic legs | 6.5 – 7.0 millimeters |
Structure of the cockroach legs
The three pairs of legs of the cockroach each have six segments that are articulating with each other. These six segments of the cockroach legs are articulating by mono or dicondylic articulation.
Most of them are the membranous articulation in the cockroach legs. Now, let’s see the six different segments of the cockroach legs with the labeled diagram.
You will find the following 6 segments in each leg of the cockroach from proximal to the distal ends –
- #1. Coxa of the roach’s leg,
- #2. Trochanter (the second segment of the roach’s leg),
- #3. The larger and longer femur of the cockroach legs,
- #4. Longest tibia segment of the cockroach legs,
- #5. Tarsus segments in the roach legs, and
- #6. Pretarsus or plantula of the cockroach legs,
Again, you will find a small curved arolium at the distal end of the pretarsus or plantula segment of the cockroach legs. All these segments of the cockroach legs are identified in the labeled diagrams.
The cockroach legs have an extensive sensory system. Some of the sensory elements of the cockroach legs are proprioceptors that monitor the position of the leg segments.
Mechanoreceptors and chemoreceptors in the cockroach legs are involved in the perception of environmental stimuli. Again, each leg of the cockroach shows a smooth and hairy pad that helps them to attach to various devices or objects.
Important muscles of cockroach legs – identification
You will find the following muscles in the cockroach legs –
- #1. Apodemes of the levator muscles that attach to the trochanter segment of the cockroach legs,
- #2. Apodemes of the depressor muscles that articulate with the coxa segment of the cockroach legs,
- #3. Extensor muscle in the distal end of the femur segment of the cockroach legs,
- #4. Flexor muscles in the distal end of the femur segment of the cockroach legs,
- #5. Apodemes of the levator muscles that articulate with the tibia segment of the cockroach legs, and
- #6. Apodemes of the depressor muscle that articulate with the tibia segment of the cockroach legs,
You will also find some depressor tarsal and pretarsal muscles in the cockroach legs. I will share these muscles from the cockroach legs in this article’s next section (leg muscle description section).
Coxa of the cockroach legs anatomy
The coxa is the basal segment of the cockroach legs that is particularly larger and well-supplied with powerful muscles. In the resting position, you will find the coxa of the cockroach legs in the mid-ventral line of the thorax.
Proximally, the coxa articulates with the portion of the thorax (prothorax, mesothorax, and metathorax). In contrast, the distal end of the coxa articulates with the proximal extremity of the trochanter.
In the American cockroach, you will see well-developed coxa in their legs. Again, the coxa of the American cockroach has well-developed posterior and anterior parts.
Here, the posterior larger part of the coxa is meron, whereas the anterior part of the coxa is known as the coxa vera. Here, the integument adjacent to the meron is semitransparent.
You will see the large coxal muscles in the meron segment of the coxa of each pair of cockroach legs.
The distal part of the coxa of the cockroach leg is in the form of a truncated cone. This part of the cockroach leg articulates with the wall of the thorax.
You may also find the single articulation of the coxa with the pleuron help them to move freely. Now, the distal part of the coxa of the cockroach leg articulates with the trochanter.
Trochanter of the cockroach legs
The trochanter of the cockroach legs is small and forms a basal joint with coxa proximally and a femur segment distally. This small segment of the cockroach leg forms the dicondylic type joint with the coxa.
You will find only the movement in the vertical plane in the basal joint between coxa and coxa. Sometimes you may find the two parts of the trochanter in the cockroach legs.
Actually, the second segment of the trochanter is part of the cockroach femur. In the trochanter of the cockroach leg, you will find two important muscles – the apodemes of the levator muscle and the apodemes of the depressor muscle.
Femur segment of the cockroach legs
The femur segment of the small type cockroach leg is somewhat narrower and small compared to the coxa. But, this femur segment is the larger and stoutest part of the leg in the larger cockroach.
The proximal part of the cockroach femur is often more or less fixed to the trochanter. You will also find the free movement in between the proximal part of the femur and the trochanter.
Typically, there are no muscles in the proximal segment of the femur of the cockroach leg. Sometimes, you may find a single muscle in the femur segment of the leg that arises from the trochanter.
This muscle of the femur will produce a slight backward movement in the cockroach leg. Again, this muscle will also produce slight flexion movement in the cockroach legs.
Tibia of the cockroach legs
The fourth division of the cockroach leg is the long slender tibia. This tibia of the cockroach especially has the covering of long bristles. These long bristles may find numerous at the distal end of the cockroach tibia.
The cockroach’s tibia is also known as the shank of the leg. It articulates with the femur by dicondylic articulation to move in the vertical plane.
Again, the head of the cockroach tibia may bend so that the shank can flex right back against the femur bone.
Tarsus and pretarsus of the cockroach legs
Next to the tibia segment of the cockroach leg, you will find five-joined tarsus. Here, the proximal division of the tarsus of the leg is much longer than the succeeding ones.
The tarsus of the cockroach is differentiated from the true segments by the absence of muscles. Here, the basal tarsomere articulates with the distal end of the tibia by a single condyle.
But, you will not find any articulation between the tarsomeres of the cockroach legs. Rather, you will find the flexible membrane here in the tarsomeres that help them to move freely.
At the tip of each tarsal segment of the cockroach legs, you will see an adhesive pad (also known as the plantula). This adhesive pad helps them to climb on slippery surfaces.
You will find some of the fine clinging tenent hairs in the adhesive pad. These tenent hairs on the adhesive pad allow them to climb on slippery surfaces.
In some cockroaches, you may find the sticky adhesive pad. The internal structure of the adhesive pad or plantula shows the internal cavity that fills with blood.
The last segment of the cockroach leg is the pretarsus. This is the small terminal segment that contains the median lobe or arolium.
Again, in this arolium or median lobe of the terminal segment, you will find the fine clinging tenent hairs like the plantula. The terminal part of this arolium also shows a pair of large curved claws.
There is a ventral unguitractor plate in the end part of the arolium on which the apodemes of the flexor muscle of the claw attach.
How many legs does a hissing or German cockroach have?
The hissing cockroach is a unique type that can make a sound. Like the ideal cockroach, you will find similar anatomical (both external and internal) facts in the hissing cockroach.
You may have the question – how many legs does a hissing cockroach have? Well, the hissing and the German cockroaches have three pairs of legs (total 6 legs) that attaches to their thorax in a similar pattern to an ideal cockroach.
So, you will find the six segments in each leg of the hissing and German cockroaches. Again, the segments of these hissing or German cockroaches’ legs possess the structure or features I have already described above in the ideal cockroach’s legs.
The tarsus and pretarsus segments of the hissing cockroaches are more sticky due to the presence of the tenent hairs. Again, the plantula and arolium are more developed than the ideal cockroaches.
Muscles of the cockroach legs
Overall the muscles help to move the legs in different directions. You will find two major types of muscles in the cockroach legs –
- Extrinsic muscles – arising outside of the legs, and
- Intrinsic muscles – remain within the legs and run from one segment to another segment,
Here, the coxa of the cockroach legs is moved by the extrinsic muscles that arise from the thorax. Okay, let’s see the major extrinsic and intrinsic muscles from the cockroach legs –
The extrinsic muscles of the cockroach legs include –
- #1. Anterior rotatory muscles from the sternum,
- #2. Posterior rotatory muscles from the sternum,
- #3. Adductor muscles from the sternum,
- #4. Abductor muscles from the pleuron,
- #5. Remotor muscles from the tergum, and
- #6. Promotor muscles from the tergum,
Now, let’s see the intrinsic muscles of the cockroach legs –
- #1. Trochanter depressor muscles of the cockroach legs,
- #2. Trochanteric levator muscles of the roach legs,
- #3. Femoral redactor muscle from the legs,
- #4. Pretarsal depressor muscle of the leg,
- #5. Tibia flexor muscle of the cockroach leg,
- #6. Tibia extensor muscle of the cockroach legs,
- #7. Tarsal levator and depressor muscles of the cockroach legs, and
- #8. Pretarsal apodemes of the cockroach legs,
The labeled diagrams identify all these extrinsic and intrinsic muscles from the cockroach legs. You will find more labeled diagrams of the cockroach legs here on social media.
Extrinsic and intrinsic muscle of the cockroach legs
The intrinsic muscles of the cockroach legs are different from those of the coxal musculature. Here, the three depressor muscles of the cockroach trochanter arise from the coxa.
The three depressor muscles originate in the coxa and pleural ridge of the tergum. Here, the cockroach tibia is moved by the extensor and flexor muscles. These extensor and flexor muscles of the tibia arise from the femur bone and insert into apodemes from the membrane at the base of the tibia.
The pretarsus of the cockroach legs possess the depressor muscle but no levator muscles. Here, the fibers of the depressor muscle occur in a small group in the femur and tibia segments.
The innervation of the cockroach leg muscles is complex and innervated by the slow and fast axons.
Sensory systems of the cockroach legs
The legs of the cockroach have extensive sensory systems. You will find two types of sensory elements in the sensory system in the cockroach legs –
- #1. Proprioceptors – monitoring the positions of the leg segments and the stance of the cockroach, and
- #2. Exteroceptors – many exteroceptive sensilla present in the legs of the cockroaches,
The proprioceptors of the cockroach leg include hair plates, campaniform sensilla, and chordotonal organs. Here, the hair plates on the cockroach legs contribute to the gravitational sense.
You will find a campaniform sensilla group on the cockroach legs trochanter. Again, you will also find the campaniform sensilla in the proximal end of the femur, tibia, and dorsal surface of the tarsomere.
Mechanosensitive trichoid sensilla are present on the cockroach legs’ different segments.
How many legs does a cockroach have – labeled diagram
In this section, I will show you the labeled diagram of the cockroach legs. Here, you will clearly understand the arrangement of the legs with their different segments from the labeled diagram.
The cockroach leg labeled diagram shows different segments (six). Here, I tried to show you the coxa, trochanter, femur, tibia, tarsus, and pretarsus segments from the cockroach legs in the labeled diagram.
Again, I showed you the different muscles from the various segments of the cockroach leg in the labeled diagram. The diagram of the cockroach legs also shows the numerous bristles on the femur and tibia segments.
In the diagram, the fine clinging tenent hairs are also identified from the tarsus and pretarsus segments of the cockroach legs. You may find more diagrams of cockroach bodies (external and internal) in different articles on insect pets.
Frequently asked questions on cockroach legs
Now, you will see the frequently asked questions on the cockroach leg’s number and its structure. But you might know the details of the number and anatomical facts of the cockroach legs I already described in this article.
Okay, let’s see the common questions on the cockroach legs that insect lovers ask –
Do cockroaches have 8 legs?
No, no cockroach has 8 (eight) legs on its body. You will find only six fixed legs in the cockroach body.
These six legs of the cockroach attach to the thorax region. Again, these legs are termed the prothoracic legs (anterior), metathoracic legs (middle), and mesothoracic legs (posterior).
You will find 8 pairs of legs in the spider; you may read more about the spider here – why is the spider not an insect?
How many legs do cockroaches have?
As I told you before, cockroaches (German or hissing or any other cockroach) have only six pairs of legs. Here, the anterior pairs of the legs are comparatively smaller than these of the middle and posterior pairs.
The anterior or prothoracic pairs of the legs attach to the anterior part of the cockroach thorax. Again, the middle pairs of cockroach legs are comparatively larger than the anterior pair.
Do cockroaches have 2 legs?
No, cockroaches don’t have 2 pairs; they possess 6 (six) pairs of well-developed legs attached to their thorax. The posterior or mesothoracic legs of the cockroach are larger and more well-developed than others pairs of legs.
Conclusion
So, I hope you got the answer to the question – how many legs does a cockroach have? The cockroach possesses six pairs of well-developed legs that attach the various segment of the thorax.
Again, the number of legs in the cockroach is fixed, each with six segments. The anatomical facts of these six segments from three pairs of legs might help you to understand their unique features.
