Eyes straight out of a cartoon, raptorial legs resembling the praying mantis, a body pattern like a wasp, and finely woven wings that would be a lacemakers dream mantispids or mantidflies are one of the invertebrate worlds lesser-known insects. Not many study them; for those who do, the mantisfly diversity and its life cycle are still secrets that are difficult to access.
Most mantispids are small, measuring less than 15 mm in length, with the largest one having a forewing length of 35 mm (Ohl, 2004). They resemble the praying mantids in having an elongated prothorax (the part of the insect where the first pair of legs is attached) and raptorial forelegs with spines that are kept folded in the typical praying mantis fashion. These features are why they have been named mantispids.
Mantispids in general are predators of arthropods and serve an important function of keeping a check on the population of several plant pests. Like the praying mantis, mantispids are also sophisticated ambush and stalking predators and this behaviour is highly dependent upon vision, and smell.
Mantispids structural and behavioral resemblances with the praying mantids beg the question: did the two coevolve? How did they get these similar features? Both are ambush hunters and rely on their sharp vision for predation. But no evolutionary connection has been found so far, with praying mantids belonging to Order Mantodea and mantispids to the Order Neuroptera (which includes lacewings and antlions). The physical similarity between praying mantis and mantispids is probably a result of convergent evolution: independent evolutionary paths resulting in similar features on unrelated species.
Some mantispids (belonging to the subfamily Mantispinae) mimic wasps. This is an example of Batesian mimicry or a biological resemblance, where a harmless organism (the mimic) starts resembling a poisonous or dangerous species, called the model. This fools predators they mistake the mimic for the model and leave it alone. Some mantispids mimic wasps from the Vespidae family, while others are known to be mimics of sphecid and eumenid wasps too.
While many believe that they are restricted in their distribution and not commonly found, this may not be true. Due to their small size, they are perhaps simply overlooked and missed. What is probably true is that it is quite difficult to find their larvae to study their life history.
Mantidflies belong to the order Neuroptera, sub-order Planipennia, superfamily Mantispoidea with three families, namely Mantispidae (mantispid lacewings), Rhachiberothidae (thorny lacewings) and Berothidae (beaded lacewings). Despite exhibiting some intriguing and distinct life histories, they remain among the poorly studied groups of insects. Of these three families, only members of Mantispidae have been discovered and studied from India. Although Mantispidae is represented by three subfamilies, only one sub-family Mantispinae is described from India.
Around 410 species belonging to family Mantispidae have been discovered till now. Only 22 species from 8 genera of Mantispidae are known from India Five species have been reported from Kerala. They belong to the genus Mantispilla, Tuberonatha, Mantispa and Euclimacia. Of these, Mantispilla indica reported by researchers T. B.Suryanaryana and C. Bijoy from Irinjalikuda, is a new record for the Western Ghats. Another new find from Calicut, Kerala is Afromantispa neptunica, a first record for the Oriental region.
Tuberonotha strenua and undescribed species of Tuberonatha and Austroclimaciella, have been sighted and photographed from Kanyakumari wildlife sanctuary and Kalakad Mundanthurai Tiger Reserve. These are unofficial identifications, as they are yet to be formally described, and the process is pending due to lack of collection permits. There are several more unidentified members of Mantispidae from the Western Ghats region of Kerala and Tamil Nadu waiting in the wings, but neither human nor financial resources are available to study them.
The most interesting aspect of mantispids is their larval development.Among the larvae, the most well studied and known are the spider hunters of Manispinae. The epithet spider-hunters comes from the larval behavior of the life-cycle of members of the subfamily Mantispinae. These mantispids exhibit hypermetamorphosis where one or more of the larval stages differ from the others during the life cycle. Mantispinae larvae feed and develop inside spider eggs!
The female mantispid lays thousands of stalked eggs. The egg stalks are made of silk secreted by the mother. The larvae that emerge from these eggs, remain at first clustered together on the silken stalk, before separating in search of spider egg cases.Vision and olfaction are believed to play an important role in locating spider eggs. It has been observed that the larva could move in the direction of the spider or its egg case from a distance.
Two strategies are adopted to locate spider egg cases. The larvae go in search of egg cases, which the spiders may have deposited on the ground. They penetrate through the silken cover to enter the eggs. Such species are attracted by the spider silk and are quite adept at burrowing through it to enter the eggs. In other cases, the larvae lie in waiting for a spider to pass, in order to climb on it. These species have a sucker with which they attach themselves to the silken stalk, waving their head and body as they wait to board a spider.
Once on the spider, the mantispids attach themselves to the spiders legs and slowly reach a position close to or on the pedicel of the spider (the stalk that attaches a spiders head to the abdomen). Why the pedicel? Because the spider can remove the larva if it rests in any other location. The pedicel is not accessible to the spider.
Another fact that the larvae have to be careful about is the size of the spider to board. For a successful future they must choose a large spider, so that they do not fall within the size of the spiders prey or become a meal for the spider or spiderlings.
Occasionally after boarding a spider, the mantispids may enter into its book lung (breathing organ) and feed on the haemolymph. More often than not, they simply travel with the spider and wait for it to lay eggs. In case they have boarded a male, they transfer themselves to the female during mating and wait for eggs to be laid. In some bizarre cases, they also board the female when it is cannibalizing the male. A single egg may be penetrated by more than one larva. In such cases, the principle of survival of the fittest operates. The mandibles and maxillae of this first instar fit together to form a piercing/sucking tube that is used to feed.
The larvae moult twice. The second and third instar lose some of the structures. They have reduced legs as they no longer need to be mobile. The simple, single-lens eyes, referred to as stemmata present in the first instar, are also lost as there is no role for vision in the rest of the development. The final instar in fact looks more like a beetle grub. As pupation begins, it produces silk to spin the cocoon.
Pupation occurs within the spider eggs. In a series of experiments done in the laboratory with Mantispa uhleri, scientists found a correlation between the size of the adult mantispid and the number of spider eggs consumed. A minimum of thirty spider eggs were found to be necessary for the whole process to be successful.
The larvae of mantispids exhibit high levels of specificity while choosing a suitable host. Members of families, not yet discovered from India, or studied in detail elsewhere, exhibit equally remarkable life histories. Larvae of the beaded lacewings, yet to be discovered from India, are voracious feeders of termites. Very little is known about the larvae of thorny lacewings that are found in the sub-Saharan regions of Africa. Symphrasinae larvae are known parasites of certain wasps; they feed on eggs, larvae and pupae of wasps. Some even mimic their hosts to avoid predation. While The larvae of Symphasinae are found associated mostly with larvae of Hymenoptera (including bees, and ants also) a few have been found, to a lesser extent, from larvae of Lepidoptera (butterflies and moths), Coleoptera (beetles) and a few Diptera (flies).
A recent study by a Ph.D. student in India led to the surprising discovery of a new host for Mantispinae larva. Along with Louwrens Snyman from South Africa, C Binoy from the University of Calicut, Kerala, as part of his research, reported for the first time a Mantispinae emerging from the nest of Sceliphron coromandelicum, a mud-dauber wasp. Symphrasines are known to be specialist brood predators targeting aculeate hymenopterans (mostly bees and ants), but this is the first time that a Mantispinae, Afromantispa neptunica has been discovered from a wasps nest. It is also a first record of the genus Afromantispa from India as this mantispid genus is generally found distributed in Afrotropical and Arabian peninsular regions.
Another oddity came from a single study outside India. A Leptomantispa pulchella larva was recovered from an adult caddisfly, Oecetis inconspicua (Trichoptera, Leptoceridae) (Hoffman & Hamilton 1988a). Such discoveries reveal how little we know about this enigmatic insect group Mantispoidea.
Adaptation of larvae is important in maximising the species success. A larvas ability to locate food, escape predation, defend against enemies and survive in given environmental conditions increases the survival rate of insect species. The separation of food sources of larvae and adult reduces competition. All these characteristics exhibited by Mantispinae make them a useful candidate for ecosystem modelling.
This article has touched upon only a few points of their lifestyle. There are many more facets to their life, worth finding out. The very fact that both adults and larvae, serve to keep a check on insect population makes them a species worth conserving. They are both visible and secretive. Their lives are both an invitation and a challenge, for humans searching for answers to survive on an increasingly hostile planet.
Kurt E. Redborg, 1998: Biology of the Mantispidae; Annual Review of Entomology Vol 43: 175-94
Snyman et al, 2020: A review of the biology and biogeography of Mantispidae (Neuroptera) Insect Systematics & Evolution. DOI 10.1163/1876312X-bja10002
Kaur et al. 2021: Subfamily Mantispinae Enderlein, 1910 (Insecta: Neuroptera) in India;Zootaxa 5068 (3): 355377. https://doi.org/10.11646/zootaxa.5068.3.2
T.B. Suryanarayanan & C. Bijoy. 2021: First record of Mantispilla indica (Westwood, 1852) (Neuroptera: Mantispidae) from the Western Ghats, India. JOTT Vol 13 No.9 19376-19379
Snyman L.P, & Binoy C. 2022: Evolutionary relic or a curious coincidence? A mantisfly emerging from a mud-dauber nest; Evolutionary Ecology; https://doi.org/10.1007/s10682-022-10167-8
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Banner image: Tuberonotha strenua. Photo by Geetha Iyer.
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Mantispids: secretive insects with lace for wings - Mongabay-India