The European mantis or Mantis religiosa is a large hemimetabolic insect in the family of the Mantidae ('mantids'), which is the largest family of the order Mantodea (mantises). Their common name praying mantis is derived from the distinctive posture of the first pair of legs that can be observed in animals in repose. It resembles a praying attitude. Both males and females have elongated bodies with two pair of wings. The most striking features that all Mantodea share are a very mobile, triangular head with large compound eyes and their first pair of legs (the 'raptorial legs') which is highly modified for the efficient capture and restrain of fast moving or flying prey.
In Germany, M. religiosa is listed as 'threatened' on the German Red List. It is not supposed to be caught or held as a pet.
Video European mantis
Anatomy
Even though female Mantis religiosa are usually larger and heavier than male individuals (7-9 cm versus 6-7 cm), the antennae and the eyes of male animals outsize these of the females. Along with the forward directed compound eyes there are also simple eyes to be found on the head. These three dorsal ocelli are also more pronounced in males than in females.
Male individuals are often found to be more active and agile whereas females are physically more powerful. One of the outcomes of these morphological variations is that only males and very young females are able to fly. Adult females are generally too large and heavy for their wings to enable a take-off.
Mantids show strong deimatic display from very early life stages on. This behavior can be observed throughout different groups of animals and is used to scare or startle potential predators in order to give the attacked animal a chance to escape. The deimatic display in M. religiosa involves wing spreading and bending of the raptorial legs to reveal two matched black eyespots with a yellow or white center at the base of the coxae (the base of the leg). It makes the animal appear much larger and more of a threat to the attacker. The black eyespots are also a distinct feature for species discrimination of the European mantis. Another unique feature of M. religiosa is its midline metathoracic ear (see Ultrasound avoidance). This "tympanal auditory organ" is an unpaired structure found on the ventral side of the animal on the metathorax between the third pair of legs. Unlike other sound-processing organs found among different groups of insects, the metathoracic ear has a high sensitivity across high and low frequencies and even ultrasound. Therefore, the authors call it a 'true ear'.
Maps European mantis
Coloration
The great variation in the coloration of M. religiosa from different shades of yellow, brown, green and sometimes black has been the cause of numerous hypotheses and studies for over one hundred years. However, no generally accepted answer about reason, benefit or mechanism of the coloration or the change of coloration has been found.
Di Cesnola observed in 1904 that green mantids were found on fresh green grass whereas brown individuals seemed to prefer brown grass which was burned by the sun. When forced to change the location so it did not longer match their coloration, almost all the 'not matching' animals were killed by predators like bird. This might indicate a camouflaging purpose of the coloration. Przibram also observed in 1907 that a change in temperature can trigger a change in coloration: animals that hatched in a cold environment turned green after moulting when heat and sunlight were provided. Without the change in temperature and only a change in the color of the background, no change in coloration occurred. This finding contradicts with Di Cesnola who claims to have observed the animals within the same time and location (and therefore the same temperature).
Distribution
M. religiosa can be found in Southern Europe, Asia, Africa, Australia and North America. There are two confirmed stable populations in Germany: one in Rhineland-Palatinate and one in Baden-Württemberg. In the last years there were more and more reports of the distribution of the animals in Northern Europe as well.
Despite being an introduced species, it is the official state insect of Connecticut.
Reproduction
The sexual behavior of praying mantids in general is curious and has therefore received a fair amount of interest from scientists over the last century. The differences between the various species are well known.
In M. religiosa, courtship and mating are separated into two steps: preliminary courtship and copulation. The preliminary courtship begins with the first visual contact between the animals and ends with the first physical contact. Copulation begins with physical contact and ends when the spermatophore is deposited:
Only a few days after the final moult into adults, the animals begin to show interest in the opposite sex--this point is marked as the achievement of sexual maturity. Males have been observed to be most attracted to females during the middle of the day when it is hottest. Theories are that the female pheromones are most volatile in the heat and that also the male, as a thermophilic insect, is most active.
Instead of just observing them, sexually mature males approach sexually mature females when then see one. But resulting out of the physical superiority of the females, male M. religiosa must face certain challenges by doing so. When a female spots a male, she is very likely to attack and kill him (see also: Sexual cannibalism). Therefore, males can be observed to be very slow and cautious in their approach: after spotting her, the male usually freezes and turns its head to look directly at her. Since the foveas in his eyes face directly forwards he so assures that he has the most accurate and detailed view of her and can watch every of her moves. He then proceeds to approach her from behind. Males can be observed to stop as soon as the female turns her head or even moves. Mantids are very good at detecting moving structures but are almost unable to see immobile objects. Using this 'stop-and-go' tactic, the male stalks closer to the female. This can often take several hours. Depending on the environment, males sometimes show a light 'rocking'-behavior which is believed to imitate the leaves of surrounding plants in order to blend in with the background. Males doing this had no higher probability of being detected and attacked which supports this hypothesis of concealment.
There has not been a mention of male of female courtship neither in the field nor in captivity. The male in fact does not win by display, he wins by the absence of display. Once the male is close enough to the female, he opens his wings a little to facilitate his jump on the females back. As soon as he lands he proceeds to hold on to her with his raptorial legs. His tibiae fit into a pair of grooves on either side of the females mesothorax in front of her wing-bases. When the male is in a secure position, copulation is initiated. The genitals, which are found on the end of the abdomen in both sexes, look quite different: the males possess a pair of asymmetrical claspers while the females have an ovipositor. The ovipositor is rather short in comparison to other insects. It is covered by part by the edges of the last sternum. The abdomen of the male curves and twists in a 90° angle around the females to insert the claspers between the ovipositor and the sternum. The abdomen of the male then contracts in a peristaltic manner. The animals can stay in this position for four to five hours before a spermatophore is deposited inside the female and the claspers are withdrawn. The male now lets go of the female to drop to the ground to get out of reach of the female for his own safety. After getting away approximately 50 cm, he stops and freezes for about four minutes before he leaves eventually. This behavior could be interpreted as necessary rest after the efforts of copulating in a safe distance from the female.
Larval development
The intervals of oviposition after copulating depend on the food intake and the overall physical fitness of the female. It takes on average eleven days for the female to form and deposit an ootheca which contains around 100 to 200 eggs. Copulation usually takes place in September or October but the eggs overwinter and the larva don't hatch until the following spring. The hatching is strongly influenced by environmental conditions like temperature (at least 17°) and humidity. Females prefer to deposit their eggs on solid substrates at warm and sunny sites. Most eggs from one ootheca hatch at the same time along the entire convex site as worm-like pre-larva (L1). The hatchings always occur in the mornings.
The L1 just exist for a very short period of time; the first moult already happens on or very close to the ootheca. The now emerging nymphs already look a lot like the adults but are maybe a tenth of their size. Very few animals (~ 10%) survive this first instar stage due to lack of appropriately sized food, low temperatures or insufficient humidity.
The L2-L6 generally last about 14 days each. During this time a growth of around 6 mm per stadium can be observed. Each stadium is completed with a moult. The L7 develops a more compact shape. Wing pads become visible. L7 and L8 show the same growth rate and duration as the previous stadia. After the next moult the adult animal emerges. It now has wings and is fully developed. While more than eight moult have never been observed in M. religiosa, females usually need one more moult than males under similar circumstances.
There are reports about closely related mantids which are larger than M. religiosa and require more moults (9-11). The fact that female animals need a longer time to develop and more moults might be due to the difference in size.
Sexual cannibalism
The phenomenon that conspecifics are attacked and eaten after, during and sometimes even before copulation is called sexual cannibalism. Many examples are known in various groups of invertebrates including the mantids. There are some speculations about the benefits of this behavior but its causes are not fully understood yet. For quite some time the belief that sexual cannibalism in M. religiosa only occurred in captivity was wide spread. It was believed that it was an artefact of improper animal keeping (too little food or space). In 1992 however, the cannibalizing behavior of female M. religiosa was observed in a field study. Lawrence compared the percentage of cannibalism in natural and manipulated (males and females were put close together in field) pairings and found rates of 31% and 24%. This proves that sexual cannibalism in this praying mantid is not caused by laboratory conditions. They can however intensify the phenomenon: females that were starved for more than three days were more likely to attack males, even before copulation. While the cannibalization before the copulation is still puzzling to scientist, there are some theories about the benefits of sexual cannibalism in general: Eating her mate provides the female with a lot of nutrients she doesn't have to hunt for. She has a prey item available that is bigger than the prey she would be able to catch in the manner she usually hunts. The meal also takes place during or shortly after she was fertilized giving her more resources for the faster production of a large ootheca with large eggs, increasing the chance of her offspring to survive. Males have also been known to be more attracted to heavier, well-nourished females for this reason.
On the first glance, however this behavior does not seem to be very beneficial for the male since he dies and can't create more offspring with his genetic material. Yet male M. religiosa usually don't get to mate more than once anyway. They have a shorter life expectancy than females (7-8 versus 11-12 days) and since food can begin to become scarce in September and October the male might starve before he has the chance to mate again. Copulation is also known to take longer when cannibalization occurs. It seems advantageous to transfer more sperm in this elongated time and additionally provide the female with nutrients. Doing this the male might just pass on his genes once but he can 'make sure' that his offspring is successful since it comes from a well-nourished female.
There is however some controversy concerning this theory. The elaborate absence of display behavior does not support this 'selfless' behavior of the males. It could have also been observed that males are more likely to approach a female which is distracted by feeding or cleaning herself. The approach is also happening a lot faster in these cases. The male seems to try to avoid his cannibalization very actively.
The fact that sexual cannibalization happens so often is surely also caused by the fact that a male without a head can continue and even initiate copulation. It is believed that the cerebral ganglion might have an inhibitory effect on copulatory reflexes. Once it is removed by removing the head, copulation might even be longer since the male can never 'decide' to let go. A couple of mantids can also start copulating when the heads of both animal get removed artificially beforehand. The beheaded animals can live for up to five days and usually just die when they bleed out or starve to death.
Hunting
M. religiosa is a carnivorous ambush predator that actively scans its environment and feeds on most insects that are not too large to be captured by rapid extension of its raptorial legs. Only living and moving prey is captured and consumed immediately using their powerful mandibles. Grasshoppers seem to be rather popular, probably because of their type of movement (flying or leaping) but crickets and cockroaches are also frequently preyed upon. The attack or consumption of Mollusca, Aranea, Myriapoda or Oligochaeta is also not unheard of. Caught prey gets trapped between the spikes on femur and tibia and is now immobilized. The mantis then starts eating the still living and preferably moving prey. Some years ago, the general opinion was that they killed their prey with a bite in the neck before consuming it but current observations can't support this: the animals just start eating the body parts which are closest to their mouths.
M. religiosa is also known to eat conspecifics outside a sexual context. Because of this they usually need to be kept isolated from each other in captivity.
Visual system
The large compound eyes that account for a great portion of the head make it quickly clear that vision seem to be important for M. religiosa. Their hunting behavior as well as their sexual interactions rely almost exclusively on sight and the detection of movement. The capture of fast flying prey out of the air would not be possible without a high level of temporal resolution. The localization of the direction and distance of the prey are crucial here.
The eyes of M. religiosa are apposition eyes with eight types of photoreceptor cells and therefore best adapted for daylight vision. One compound eye of an adult mantid consists of 8.000 to 10.000 optically isolated ommatidia with an interommatidial angle of 2° in the periphery and 0,7° in the fovea. Interommatidial angles in insects go from tens of degrees to 0,24° in dragonflies which puts the mantids on the upper end of spatial resolution. The overlap of the visual field of the two eyes is 40° in nymphs and up to 70° in adult animals.
The pseudopupil, a small dark region in the eye is rather conspicuous. It moves when the animals head is moving and represents the area of parallel ommatidia which absorb the incident light and therefore appear darker than the rest of the eye.
The peering behavior that can be observed in M. religiosa is believed to be essential for the measurement of distances and depth perception: a site-to-site pendulum like movement of the head or the whole body in a horizontal plane is used to scan the environment. Motion parallax is a depth cue that describes the fact that the closer and object is, the faster it seems to move when turning your head while looking at it compared to slower moving objects which are more distant. Animals that were blinded on one eye did not strike for prey proving that binocular vision is essential since the disparity between the information of each eye is used to estimate distances as well.
The development of the visual system was reviewed by Karl Kral in 2014: while high contrast cues could be perceived by adults and nymphs (two hours to three days) alike, the differentiation between lower contrast cues was much less successful in the two hour old animals. There was however a great improvement after only three days of life. The eyes of newly hatched animals are less than half the size of the eyes of adult animals and have fewer ommatidia. Also, the facets of the frontal ommatidia which are usually used for the detection of partners and prey are not enlarged yet. While they already have all the necessary structures, very young animals have a restricted visual field and lower resolution and sensitivity to light. The great improvement of vision after only three days happens due to the sclerotization of the cuticle which includes the corneal lenses of the ommatidia. The improved lenses are not able to focus the light on the retina. There have been a few remarkable new findings concerning the visual system of different mantid-species like Sphodromantis lineola: using 3D-glasses and a 3D-cinema on the insects, stereopsis could be demonstrated. It would be worth to consider to conduct comparable experiments with M. religiosa since the two species are rather closely related.
Subspecies
- Mantis religiosa beybienkoi found in Kazakhstan, Tajikistan, Mongolia and West Siberia, Primorsky Krai (Russian Far East)
- Mantis religiosa caucasica found in Stavropol
- Mantis religiosa eichleri found in Ethiopia, Mauritania, Niokolo-Koba, Ghana, Cameroon, Kenya, Congo, Niger, Senegal, Somalia, Sudan, Tanzania, Togo, Zimbabwe, Burkina Faso, Zambia and Anatolia
- Mantis religiosa inornata found in India, Iran, Nepal, Pakistan
- syn. Mantis religiosa akbari (Soomro et al., 2001)
- syn. Mantis inornata (Werner, 1930)
- Mantis religiosa langoalata found in Uzbekistan
- Mantis religiosa latinota found in Kazakhstan
- Mantis religiosa macedonica found in Macedonia
- Mantis religiosa major found in Mombasa (Kenya)
- Mantis religiosa polonica found in Poland, Russia
- Mantis religiosa religiosa found in Africa, North America: Canada, United States, Europe, Asia: Nepal, but not in South America or Australia
- syn.Mantis religiosa maroccana (Thunberg, 1815)
- syn.Mantis religiosa radiata (Fischer-Waldheim, 1846)
- syn.Mantis religiosa sancta (Fabricius, 1787)
- Mantis religiosa siedleckii found in Southeast Asia: Taiwan, Thailand, Malaysia, Java, Sulawesi
- Mantis religiosa sinica found in China, Japan, South Korea, Vietnam
Additional images
References
External links
Data related to Mantis religiosa at Wikispecies
- Photographs of European Mantis (Mantis religiosa)
- A European Mantis feeding on a variety of insects
Source of article : Wikipedia
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