Praying mantids: the queens of mimicry

Praying mantids (more commonly known as mantises) have been beloved and feared by different cultures throughout history. They are agile, strong and specially inconspicuous insects: their great ability to mimic different elements that surrounds them and camouflage both in color and shape with the environment make them beautiful and terrifying insects at the same time… for other insects.

Throughout this article, you will learn more about the origin, ecology and also about some interesting curiosities that make this one of the most loved group of insects among entomologists worldwide.

Introduction: Origin

The term “praying mantis” is frequently used to talk about insects that belong to Mantodea order, which has about 2300 described species worldwide nowadays. This name was given them because of the pose their raptorial forelegs adopt when being relaxed: both gathered and close to the body in an angle that resembles arms in a praying pose. On the other hand, the term mantis derives from the ancient Greek term mántis = “prophet or diviner”.

Mantis europea (Praying mantis) (Picture by Katja Schulz on Flickr, CC).

Most people tend to use the term “praying mantis” to talk about any species of mantises, but the truth is that “praying mantis” is the name of a unique species (Mantis is the name of a genus inside the Mantodea order), so the properly common name for these organisms would be “mantids” or just “mantodea”.

The first fossil remains of Mantodea insects date from more than 135Ma (Baissa, Siberia). They would be closely related to termites (Isoptera order) and cockroaches (Blattodea order) according to the great similarities found on their female reproductive systems, and less closely related to grasshoppers and crickets (Orthoptera order). They are usually confused with stick insects (Phasmatodea order) and especially with mantidflies or mantispids (Mantispidae, Neuroptera order), which have raptorial forelegs like mantids.

Stick insect (Phasmatodea) (Picture by David Panevin on Flickr, CC).

Mantidfly (Picture by Ken-Ichi Ueda on Flickr, CC).

How do we recognize them? 

Despite of the existence of differences between different species, all mantids share the traits that follow:

• Elongated body (10-200mm).

• A pair of claws or raptorial forelegs with one or two rows of spines along the femur and the tibia. The spines point to different directions, so that they fit together when the claws are closed. Thus, the preys that mantids hunt will face lots of difficulties to run away. This process of catching a prey is done at high speeds, so it’s quite impossible to see it at first sight.

Mantodea forelegs (here we can see the rows of spines we mentioned above) (Public domain).

• Generally, they have two pair of wings, although some species are wingless or have suffered a reduction of their wings. Most of species of mantids have winged males, while females tend to develop reduced wings or even being wingless. Despite of these differences, it’s hard to differentiate between male and female mantids (we must count the number of body segments).
  

• Forewings are lightly hardened to protect membranous hindwings which they use to fly. Mantidflies (which we talked about on previous sections) can be distinguished from mantids because they don’t perform a process of hardening of their forewings.

Scheme of an specimen of Blepharopsis mendica or thistle mantis (Fam.Empusidae), which has both hardened forewings and membranous hindwings unfolded (Public domain).

• Mobile and triangular head that stands over an elongated thorax that reminds a neck. This neck allows mantids rotate their head 180º (this is a unique phenomenon among insects), which is essential for them to sense their environment.

• Big complex eyes capable to perceive colors and three ocelli or simple spots in the middle of their head forming a triangle. Ocelli are simple eyes formed by only one lens that are only capable to detect changes in light intensity. They usually appear in groups of three making a triangle in the frontal part of the head of many insects, and almost always located between the complex eyes.

Head of an specimen of Mantis religiosa. We can appreciate the complex eyes and the three ocelli in the middle of the forehead (Picture by David Panevin on Flickr).

• Filamentous or filiform antennae. 

How do they live?

Ecology of the group

Having an elongated body and a pair of raptorial forelegs responds to a predatory style of life: mantids remain immobile and in silence waiting their preys over different vegetable element of their environment (such as leafs, flowers, branches, etc.); it is because of that that some species of mantids have evolved in color and shape to resemble or mimic elements of their environment, which allows them to be unnoticed to preys and potential predators (we’ll talk about this issue in the last sections).

Mantids are generalist carnivorous, so they feed on a great variety of insects that they stalk and hunt at high speeds. Sometimes, it has also been observed a cannibalism behavior among specimens of the same species (or even different species).

In this video, you can watch a mantid hunting a prey. It’s very fast!

Although they can be found around the world, the major proportion of species of this order is located in tropics and in temperate emplacements. They are rarely found in cold environments or in permanent frosted places (they’re absent in Antarctica).

Life cycle

The mating process of these insects is direct, that is, a true copulation where the male has to introduce the sperm directly inside the female body.

All of us have listened about females mantids eating their mates during mating as a type of radical cannibalism. However, entomologists have recently put this into context, so it’s not a phenomenon as usual as we may think: even when it’s a true fact, most of the times this canibalism has been observed in the laboratory and not in the wild. Recent studies consider this phenomenon is a natural response of females that face difficulties that can put in danger their offspring, such as lack of resources or other types of stress sources.

After mating, the female produces a softy ootheca (a capsule with a lot of eggs) with hundreds of eggs. Oothecas have a great water content that avoid eggs being dehydrated, so they are protected from environmental dryness. Later, the ootheca hardens and turns into some kind of shell. A month later, youth mantids (also known as nymphs) hatch and grow until they reach the adult winged phase (hemimetabolous development). If you want to know more about this type of development, take a look at my previous article: “Why do insects metamorphose?”.

Ootheca (Picture by John Tann on Flickr, CC).

Diversity and mimicry

Mantids form a very diverse group of insects. There have been registered about 430 genus and 2300 species more or less in a total of 15 families. Of these 15 families, Mantidae is the one that includes the greatest number of species (inside of which we find the species Mantis religiosa). One of the most representative families of mantids in the Mediterranean region is Empusidae, whose major representative is Empusa pennata (or conehead mantis), an species exclusively located in the western Mediterranean. Empusa pennata has a similar morphology to Mantis religiosa, but they sometimes differ in size.

Specimen of Empusa pennata (Picture by Guilles San Martin on Flickr, CC).

Almost all mantids, regardless of the family they belong to, show a cryptic coloring body that allow them to being unnoticed by other organisms, both preys and predators.

The color of the body of this Mantis religiosa allows it to camouflages among leaves (Source: pixabay.com, public domain).

Some species of mantids resemble a lot to different elements of their environment because they have suffered great modifications along their evolutionary history; thus, they become able to mimic elements of their environment. This is the case of the orchid mantis (Hymenopus coronatus, fam. Hymenopodidade), a species located in rainforests of Malasia, Indonesia and Sumatra whose color and shape reminds of orchids. They always remain over orchids to stalk their preys.

Orchid mantis (Hymenopus coronatus) (Picture by Frupus on Flickr, CC).

Another stunning case: the ghost mantis (Phyllocrania paradoxa, fam. Hymenopodidae), whose shape reminds of decayed leaves (these mantids tend to stand over dead leaves). Or Deroplatys truncata (fam. Mantidae), which resembles a leaf.

Ghost mantis (Phyllocrania paradoxa) (Picture by Steve Smith on Flickr, CC).

Deroplatys truncata (Picture by Bernard DUPONT on Flickr, CC).

Moreover, a lot of species possess colored expansions or decorative elements they unfold as warning signs or for looking bigger when they face predators or other mantids.

Devil’s flower mantis (Idolomantis diabolica) in a defensive pose (Source: photo.net, Picture by Igor Siwanowicz).

Myths and curiosities

Since ancient times, the mantids have undergone multiple symbolisms. From the literature, history to religion and even martial arts, mantids have had different leading roles.

Mantis pose from kung fu (Source: chinawhisper.com).

One of the first historical references of mantis through history is recorded in the ancient Chinese dictionary called Erya (300bC), where mantids are described as symbols of courage and intrepidness. Later, many authors would talk about mantids in their works, both from a scientific point of view, as poetic and philosophic.

On the other hand, religion and mythology would have their contribution too. The Southern African indigenous mythology refers to mantids as deities in Khoi and San traditional myths. In fact, the term to denominate the mantids in Afrikáans is Hottentotsgod, which means “a god of Khoi“. On the other hand, ancient Greeks saw them as diviners or prophets with supernatural powers and also with the ability to show lost travelers the way back home. Even in ancient Egypt there existed a minor deity with mantis shape that assisted in the function of guide the deaths to the other world.

Nowadays, mantids are one of the most commercialized insects as pets. Moreover, due its hunting abilities they have been sometimes used in biological pest control.

The european mantis (Mantis religiosa) have been introduced in different regions worldwide as an agent in biological pest control. The republican island of Dominica sold these seals in 1988.

REFERENCES

• Amateur Entomologists’ Society – Praying mantids (Order: Mantodea).
• General Entomology (NC State University) – Mantodea.
• National Geographic – Praying mantids.
• Tree of Life Web Project – Mantodea.
• David M. Martill, Günter Bechly, Robert F. Loveridge (2007). “The Crato Fossil Beds of Brazil: Window into an Ancient World”. Cambridge University Press.
• Katherine L. Barry, Gregory I. Holwell, and Marie E. Herberstein (2008). “Female praying mantids use sexual cannibalism as a foraging strategy to increase fecundity”. Behavioral Ecology doi:10.109, Australia.
• Commonwealth Scientific and Industrial Research Organisation (CSIRO) – Mantodea: Praying Mantids.

Main picture from veoverde.com.

Flying made insects more diverse

The appearance of insect wings represented an adaptive improvement in the evolutionary history of these organisms, since they allowed them to spread and diversify across all kind of habitats. It is precisely for these events that wings are very diverse organs which have undergone a lot of changes.

In the following article, I will talk about the appearance of wings as elements that have ensured the diversification of insects, and also about the evolution of these organs and about their subsequent changes.

Introduction

Insects form the most diverse and successful group among the current fauna, and they’re also the unique invertebrates capable to fly. Even though they almost haven’t change since their appearance during the Devonian era (395-345Ma), the appearance of wings and of the ability to fly (alongside with other events that took place at the same time) allowed them to diversify rapidly.

Timeline of geological eras. Hexapoda and also insects appeared during the Devonian era (Picture from buglady.org).

Nowadays, there are almost 1 million of species of insects identified, and it’s known that there are lots of them waiting to be identified.

When winged insects appeared?

As you probably know, not all insects worldwide have wings: there are apterous insects (that is, insects without wings), which form the Apterygota group, and winged insects or Pterygota (is interesting to say that some organisms of this group have lost their wings later).

The most ancient winged insect is probably Delitzchala bitterfeldensis, an organism from the Palaeodictyoptera group dated from early Carboniferous in Germany (50Ma after the appearance of insects during the Devonian era, more or less).

Approximated representation of a Palaeodictyoptera. In contrast with current insects, these ones had three pair of wings instead of only one or two (the first one was probably a couple of little lobes located near the head) (Picture from Zoological excursions on Lake Baikal).

However, the fossil remains of the most ancient insect known nowadays, Rhyniognatha hirsti (dated from the early Devonian in Scotland, which was found in the “Rhynie Chert” sedimentary deposit), which has no wings, reveal that this insect shares some traits with winged insects (Pterygota). According to this, the origin of insect wings could be more ancient (probably from the Devonian or even more ancient).

We are still far from knowing the exact moment when the appearance of winged insects took place. But, despite of this, we can affirm that the ability to fly allowed them to reach new habitats, looking for more and better food and also run away from predators more easily. These events have provided a huge evolutionary advantage to insects and allowed them to diversify.

How did wings appeared?

Discrepancies toward the origin and evolution of insect wings is not limited only to “when ” , but also “how”: How did they appeared? Which structures from ancient insects have been modified to become wings?

There exist 4 hypothesis that try to explain the way wings were formed from different ancient organs: branchial hypothesis, stigmatic hypothesis, parapodial hypothesis and paranotal hypothesis.

First of all, and in order to understand all these hypothesis way better, we need to know the basis of corporal structure of insects. Let’s see the body scheme of a cricket (Orhoptera order):

Body scheme of a generic insect. There are 3 principal segments: 1) Head, where central nervous system and feeding functions are located, 2) Thorax, which has a locomotor function (here we can find all the appendices, including wings in winged insects); it’s divided in three parts: prothorax, mesothorax and metathorax; 3) Abdomen, in this segment we can usually find all the visceral organs. Moreover, we can also find the spiraculi located at both soft sides of its body, that is, holes that connect with the tracheal system and through where the exchange of gases takes place (Picture from Asturnatura).

 

Representation of the tracheal or respiratory system of an insect. This system is branched into the organism (Picture by M. Readey, Creative Commons).

 

So now, which are these hypothesis?

1) Branchial hypothesis 

According to this hypothesis, ancient Pterygota insects were aquatic organisms that were derived from terrestrial insects that got adapted to live underwater. Those ancestors breathed, as current insects, through spiracles connected to a net of internal pipes or tracheas. During the adaptation process to aquatic environment, these insects developed branchial or gill sheets on those spiracles in order to breathe underwater. Then, when they migrated back from aquatic to terrestrial environment, these sheets lost their ancient function and became a kind of wings.

According to recent data, it’s considered one of the most plausible hypothesis.

2) Stigmatic hypothesis

In the thoracic region, that is, where legs and wings born, the respiratory spiracles tend to be closed. According to this hypothesis, wings could be tracheal pipes expeled to the outside of the body in the thoracic region.

3) Parapodial hypothesis

This is a very simple hypothesis: it tells us that wings were formed by modified legs.

4) Paranotal hypothesis

A few years ago it was considered the most  plausible hypothesis, but now it competes with the brancial hypothesis. This is the most accepted hypothesis about the origin of insect’s wings. According to this hypothesis, wings were formed by the expansions of the tegumentary membrane located at both sides of the body, that is, the space located between the dorsal and the ventral surface of the body.

The expansions are known as “paranotes” (these structures gave the name to the paranotal hypothesis).

Ancient vs modern: Paleoptera and Neoptera

Nowadays, mostly of insects presents only one or two pairs of wings located, respectively, in the mesothorax and in the metathorax (middle and posterior segments), and not three pairs, as ancient insects usually had.

The way the two pairs of wings are articulated with the thorax, together with their position, allow us to differentiate two main groups of winged insects or Pterygota: Paleoptera and Neoptera.

Paleoptera

Generally, the Paleoptera insects can’t fold up the wings over the abdomen (this is an ancient condition). Moreover, the two pairs of wings are similar both in size and function, and also in the disposition of the veins that travel under their surface. Inside this group we find organisms from the Ephemeroptera order (for more information, take a look to my article about bioindicators), from Odonata order and also from the Palaeodictyoptera group, now extinguished.

An specimen of Odonata with its four wings unfolded because it has no way to fold up them over the abdomen (Picture by Ana_Cotta on Flickr, Creative Commons).

Neoptera

This group contain the rest of winged insects. Contrary to the ones explained above, Neoptera insects possess articulations that allow them to fold up the wings over the abdomen. Moreover, their wings are not always equal , and they can develop another functions (and new ones as well).

The wings of many groups of Neoptera insects have undergone a lot of secondary modifications, which allowed flying insects to diversify even more. Next, I will talk you about these secondary modifications.

An specimen of Diptera with its wings folded over its abdomen thanks to their articulations (Picture by Sander van der Wel on Flickr, Creative Commons).

Secondary modification of Neoptera’s wings

Generally, one of the two pairs of wings assumes the flying function (the ‘main wings’) while the other pair subordinates to the main one. This subordination can be expressed in two ways: 1) without external modifications (the subordinated pair of wings is limited to assist the main pair during the flight), 2) with secondary modifications, so the modified wings assume a new function.

Some Neoptera insects have undergone drastic modifications in one of the two pairs of wings. Let’s see some examples:

COLEOPTERA (beetles): the forewings, known as elytra, are a very hard structures that protect the rest of the body when they’re folded up. In this case, the hind wings are the main ones, so they assume the function of flying.

An specimen of a longhorn coleopter taking off. In this picture we can appreciate the forewings transformed into elytrum and the hind ones assuming the flying function (Picture by Matthew Fang on Flickr, Creative Commons).

HETEROPTERA (greenflies, cicadas, bedbugs): the forewings, known as hemelytra, aren’t completely hardened as in the case of beetles: only de proximal part is hardened, while the distal part has a membrane texture.

An specimen of Kleidocerys reseda (Picture by Mick Talbot on Flickr, Creative Commons).

POLINEOPTERA: in both cases that I’ve explained above, the hardening process of the forewings entails the loss of their veins; in Polineoptera insects (for example, cockroaches), the forewings are harder than the hind ones, but they retain their veins.

An specimen of Periplaneta americana (american cockroach). Its wings are plenty of veins (Picture by Gary Alpert, Creative Commons).

DIPTERA and HIMENOPTERA (flies and mosquitoes; wasps, bees and ants): in this case, the forewings assume the flying function; on the other hand, the hind wings get reduced or modified, and sometimes they don’t appear. The hind wings of flies became equilibrium organs, the halteres.

An specimen of crane fly (Tipulidae). The halteres (red circle) are located behind the forewings (Public domain picture).

ALTRES MODIFICACIONS: we can also talk about the changes in the shape, color, presence of filaments or scales, or even about the variations according to sex, hierarchy or geography location (for example, thats the case of ants or termites).

.              .             .

The origin and evolution of insect wings is still a fact waiting to be solved. Even so, independently of the moment and the way this event took place, is undeniable that wings have become key organs for the evolution and diversification of insects.

REFERENCES

• Notes taken from the subject “Biology and Diversity of Arthropodes”. Environmental Biology Degree (Universitat Autònoma de Barcelona).
• Rivas P., Martínez M.L. Paleontología de Invertebrados. Sociedad Española de Paleontología, Instituto Geológico y Minero de España, Universidad de Oviedo, Universidad de Granada. IGME, 2009.
• Information about fossils: palaeos.com.
• Vargas P., Zardoya R. El árbol de la vida: sistemática y evolución de los seres vivos. P. Vargas Gómez, 2012.

Top picture by USGS Bee Inventory and Monitoring Lab (Creative Commons).