Pensoft blog - Part 103

30th anniversary of Symposia on Chysomelidae celebrated in a new leaf beetle-themed issue

For the last 30 years entomologists all over the world have been gathering together on a regular basis, led by their fascination with one of the three most captivating with their colours and numbers beetle families. The most cardinal of these gatherings is the Symposium on Leaf Beetles, nowadays organised every two years, which traditionally culminates into special issues to hold the quintessence from the findings, talks and debates and keep them safe for the future generations. For a fifth time in a row, the latest volume is published in the open-access journal ZooKeys.

The present volume, assembled with the works of a large multinational research team and put together by editors Drs. Michael Schmitt, Ernst-Moritz-Arndt-Universität, Jorge Santiago-Blay and long-year head of the community of leaf beetle researchers, Prof. Pierre Hippolyte Auguste Jolivet, continues the seemingly ever-going task assumed by the community to further build on the knowledge about the taxonomy, distribution, physiology and biology of the amazing creatures.

In light of the news of Prof. Pierre Jolivet’s resignation from his post as head and senior editor of Research on Chrysomelidae, his colleagues and friends from the chrysomelid community have dedicated the present volume to their “spiritus rector”. “We, editors, many authors, and publishers of Research on Chrysomelidae are grateful for Pierre’s permanent intellectual stimulation, his helpful input, and his friendship,” read the final words of the editorial.

Apart from the activities linked to Research on Chrysomelidae, Prof. Pierre Jolivet has been the inspiring leader of the community of leaf beetle researchers for more than half a century. Furthermore, the Normandy-born entomologist has also published works on ants, ant-plant interactions, parasites of insects and even broader topics, such as evolution.

However, with its 30-year legacy the collaborative global initiative does not seem anywhere close to its slowing down. While a sixth consecutive volume of RoC is currently in production with ZooKeys journal, more and more young chrysomelidologists join the community. Meanwhile, the Symposia themselves having been held every four years, now take place every twenty-four months.

“Eight symposia on Chrysomelidae have been held. Many new things have been found but some problems remain unsolved,” conclude the editors.

“It is certain that some areas need more investigation, as Madagascar for instance, and that there remain many biological problems to be solved or to be discovered,” they point their next steps. “Deforestation reduces the number of species and genera, and many will disappear before being described. Few will persist as fossils in the tropics. Millions of insects have existed in the past and will remain unknown forever.”

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Original source:

Jolivet P (2015) Together with 30 years of Symposia on Chrysomelidae! Memories and personal reflections on what we know more about leaf beetles. In: Jolivet P, Santiago-Blay J, Schmitt M (Eds) Research on Chrysomelidae 5. ZooKeys 547: 35-61. doi: 10.3897/zookeys.547.7181

Research on Chrysomelidae 5 Special Issue is available to read and order from here.

Three new fishing snake species fished out of the Andean slopes in South America

Commonly known as fishing snakes, the Synophis genus has been expanded with as many as three new species following a research in the Andean cloud forests of Amazonian Ecuador and Peru. Not only is the discovery remarkable due to the rarity of new snake species being discovered, but also because this is the first time this mysterious and already eight-member genus is recorded from Peru. The study is published in the open-access journal ZooKeys.

The three new species have been identified as a result of both field and laboratory work, undertaken by Dr. Omar Torres-Carvajal, Museo de Zoología QCAZ, Ecuador, in collaboration with herpetologists from Peru (CORBIDI) and the United States (Francis Marion University). The new species differ from their closest relatives in scale features, male sexual organs and DNA. The unusual discoveries took place in areas within the 1,542,644 km2 of the Tropical Andes hotspot, western South America.

Although they are commonly known as fishing snakes, these reptiles most likely do not eat fish. Their diet and behavior are poorly known. So far, it has only been reported that one species feeds on lizards.

The fishing snakes have long been known to live in cloud forests on both sides of the Andes of Colombia and Ecuador. Yet, it seems they have waited all along to make an appearance. The new species described herein, along with a recent description of one species from southwestern Ecuador also published in Zookeys, has duplicated the number of species of fishing snakes from four to eight over the span of several months.

During their recent expeditions to several localities along the Andes of Ecuador and Peru the authors collected several individuals of fishing snakes, which they suspected to be previously unknown. After comparing their specimens with those deposited in a number of natural history museums, the authors’ suspicions only became stronger.

Consequently, the scientists examined the male snakes’ sexual organs (hemipenes) and DNA evidence. The results left no doubts that the specimens belonged to three undescribed fishing snake species.

“We started working with fishing snakes a year ago as new specimens were collected in poorly explored areas of the Amazonian slopes of the Andes in Ecuador and Peru,” explains lead author Dr. Omar Torres-Carvajal. “At that time only four species of fishing snakes had been described, and they were recognized in the literature as one of the most rare and secretive groups of snakes in South America.”

“In less than a year, we and other herpetologists doubled the number of known species of fishing snakes, showing that their diversity had been greatly underestimated,” he points out.

“This story is similar to the story of the woodlizards (Enyalioides), a group of dragon-like lizards with more than half of its species discovered in recent years in the tropical Andes,” the scientist reminisces.

“This tells us that this hotspot is more diverse than we thought, so it is very important that basic biodiversity research is properly funded,” Dr. Torres-Carvajal concludes. “Otherwise, we might never know what other scaly creatures are crawling around us.”

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Original source:

Torres-Carvajal O, Echevarría LY, Venegas PJ, Chávez G, Camper JD (2015) Description and phylogeny of three new species of Synophis (Colubridae, Dipsadinae) from the tropical Andes in Ecuador and Peru. ZooKeys 546: 153-179. doi: 10.3897/zookeys.546.6533.

Tramp ant caught globetrotting under false name

A century-old mystery surrounding the origin of an invasive ant species was recently solved by an international team of scientists. Since 1893, when it was first discovered as an invasive species in the Canary Islands, entomologists have been debating where this mystery species came from. While some insisted on the Mediterranean, some proposed Arabia and others argued for Africa. The correct answer? Asia.

The authors of the study, published in the open-access journal ZooKeys, solved the taxonomic puzzle by fitting together disparate pieces of evidence. “I was having a terrible time trying to distinguish this one Asian species from the mysterious ant that was coming in on shipments from the Caribbean, Europe and Africa,” says Dr. Eli Sarnat, University of Illinois, about his research at the Smithsonian on tramp ants that were intercepted at US ports.

Tramp ants, many of which are pest species, are spread across the globe by stowing away in the cargo of ships and planes, thus posing rising environmental, food security and public health concerns.

The same day Sarnat was working on the mysterious ant in the Smithsonian, he received an email from Dr. Evan Economo, Okinawa Institute of Science and Technology (OIST). Economo and Dr. Georg Fischer, also affiliated with OIST, had included Madagascar samples of the species in a genetic analysis, and the results unexpectedly placed it within a group of Asian species. The closest genetic match to the enigmatic ant turned out to be the very same Asian species that Sarnat had found in the Smithsonian collection.

The last piece of the riddle was discovered thanks to the painstaking work of Dr. Benoit Guénard. Guénard, a professor at the University of Hong Kong, had spent years mapping the global distributions of every ant species known to science. When he compared the ranges of the mysterious ant with the common Asian species, the two fit together like a jigsaw puzzle.

Evidence gathered from classic taxonomy, modern genetic analysis, and exhaustively researched distribution maps all pointed to the same conclusion.

“What had long been considered two different species — one found across a wide swath of Asia and the other a tramp species spread by humans across Europe, Africa, the Americas and Australia — are actually one single supertramp species,” Economo explained. “It is striking that we had these two continental super-common invaders with almost entirely complementary ranges right under our noses, yet until now no one noticed they were actually the same species,”

Original source:

Sarnat EM, Fischer G, Guénard B, Economo EP (2015) Introduced Pheidole of the world: taxonomy, biology and distribution. ZooKeys 543: 1-109.doi: 10.3897/zookeys.543.6050

Additional information:

This work was supported by USDA APHIS Identification Technology Program (13-8130-1439-CA), subsidy funding to OIST, and NSF (DEB-1145989). This work was supported by USDA APHIS Identification Technology Program (13-8130-1439-CA), subsidy funding to OIST, and NSF (DEB-1145989).

Lava attraction: 74 new beetle species found hiding in plain sight on a Hawaiian volcano

Confined to the limits of Haleakala volcano, Maui Island, Hawaii, the beetle fauna there turns out to be not only extremely diverse, but very abundant as well. When Prof. James Liebherr of the Cornell University Insect Collection thoroughly sampled beetle populations on the volcano, he identified 116 species of round-waisted predatory beetles, including 74 new to science. The taxonomic revision, complete with descriptions of the new species, is now published in the open-access journal ZooKeys.

The present discoveries and observations are certainly surprising due to their scale, even though it has been long known that the Hawaiian Islands support disproportionately high levels of biodiversity. For this group of native round-waisted beetles, called Mecyclothorax in the zoological naming system, there are 239 species across the Hawaiian Islands, all of them descended from a single colonizing species.

The 116 species known from Haleakala make that volcano the center of biodiversity for this group within Hawaii. These beetles’ evolution during the 1.2-million-year lifespan of Haleakala volcano means they have speciated faster than most organisms on Earth, including the Hawaiian Drosophila and the cichlid fishes of eastern Africa.

No less striking is the fact that the 74 newly described beetle species previously evaded discovery within the limits of Haleakala’s 1,440 km2 of surface area. Reasons for this include the restricted distributions of many of the beetle species, and the previous lack of comprehensive field sampling. During his research, Prof. Liebherr examined all quarters of the mountain to eventually find many places of 1′ latitude × 1′ longitude where more than 20Mecyclothorax species lived closely together within a limited area of forest.

Most of these diverse microhabitats were discovered in windward rainforests. Moreover, different forest areas, geographically isolated from each other by volcanic lava flows, steep valleys, or extensive mudflows, supported different sets of species. “Haleakala volcano is a large pie with different sets of beetle species living in the different slices,” comments Prof. Liebherr. “Actually the different pie slices are just like the original Hawaiian land divisions called ahu pua’a, showing that the Hawaiian people had a keen sense for how their island home was organized.”

Additionally, the round-waisted beetle species seem to thrive across a wide range of altitudes, with their populations covering the major part of the mountain’s height. Historical as well as modern records have identified representatives of these insects from 450-metre elevation up to the volcano’s summit at 3000 m. However, given land conversion and the influx of alien invasive plants, habitats below about 1000 m have been seriously disrupted, and these elevations support few native beetles.

Looking to the future, Liebherr points out that “the substantial level of sympatry, associated with occupation of diverse microhabitats by these beetles, provides ample information useful for monitoring biodiversity of the natural areas of Haleakala.”

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Original source:

Liebherr JK (2015) The Mecyclothorax beetles (Coleoptera, Carabidae, Moriomorphini) of Haleakala-, Maui: Keystone of a hyperdiverse Hawaiian radiation. ZooKeys 544: 1-407. doi: 10.3897/zookeys.544.6074

Huge organs defy austerity for tiny cave snails in the subterranean realm

While most of the knowledge about tiny snails comes from studying empty shells sifted out from piles of dust and sand, the present research is the first contemporary microscopic exploration of organs in cave snails tinier than 2 mm. The paper, published in the open-access journal Subterranean Biology, reveals that underneath the seemingly fragile shells of the Zospeum genus, there are strikingly huge organs.

A number of remarkable observations such as an enormous kidney, grooved three-pointed teeth and a huge seasonally present penis are reported in the recent study, conducted by Adrienne Jochum, Naturhistorisches Museum der Burgergemeinde Bern, Switzerland, and her international team of researchers from University of Bern, Switzerland; Shinshu University, Japan; Universitaetsklinikum Giessen und Marburg GmbH, Germany; Justus-Liebig University Giessen, Germany; University of Ljubljana, Slovenia; University of Bern Goethe-University Frankfurt, Germany; Ruhr University Bochum, Germany; Croatian Biospeleological Society, Croatia and University Duisburg-Essen, Germany.

The scientists describe these characteristics as adaptations the miniature creatures have acquired in order to survive austerity in the subterranean realm.

Usually, adaptations to cave life can include blindness or lack of eyes, loss of pigmentation, sensitivity to changes in temperature and humidity, a high starvation tolerance, or anatomical compromises such as small size and transparent shells. The present study shows that miniscule carychiid subterranean snails have developed huge organs to tolerate the unique conditions of cave life.

“Studying adaptations in extreme environments such as those found in snails of subterranean habitats can help us to understand mechanisms driving evolution in these unique habitats,” explains the first author.

Glassy cave-dwelling snails known only from Northern Spain, the southern Eastern Alpine Arc and the Dinarides might have tiny hearts, but their enormous kidney extends from one to two thirds of the total length of their minute shells. This phenomenon could be explained as an effective mechanism used to flush out large amounts of excess water during flooding seasons in caves.

The same impressive creatures have also developed elaborate muscular plates, forming the girdle that surrounds the gastric mill (gizzard) in their digestive tract. The muscular gizzard grinds the grainy stew of microorganisms and fungi the snails find in moist cave mud. These mysterious creatures graze stealthily using an elastic ribbon (radula), aligned with seemingly endless rows of three-pointed, centrally-grooved teeth, as they glide through the depths of karst caves while searching for food and partners.

Deprived from the hospitable aspects of life we have grown used to, some of the snails discussed in the present paper have evolved their reproductive system in order to be able to reproduce in the harshest of environments, even when they fail to find a partner for an extended period of time.

As a result, not only are these snails protandric hermaphrodites, meaning that they possess male sexual features initially, which later disappear so that the female phase is present, but they have a large retractable, pinecone-shaped penis for instantaneous mating in the summer when mating is most probable. To guarantee offspring, a round sac, known as the receptaculum seminis, stocks sperm received from a partner during a previous mating and allows them to self-inseminate if necessary.

Teeth in these cave snails are also described using histology for the first time. They bear a median groove on the characteristic cusps known for the Carychiidae.

Sketchy, past dissections provide the current knowledge upon which the findings from this investigation are based. Otherwise, historical descriptions of these tiny snails are only known from empty shells found in samples of cave sediment. The genus Zospeum can only be found alive by inspecting cave walls using a magnifying glass.

“Knowledge of their subterranean ecology as well as a “gut feeling” of where they might be gliding about in their glassy shells is necessary to find them,” comments Adrienne Jochum. The authors also emphasize that this groundbreaking work is important for biodiversity studies, for biogeographical investigations and for conservation management strategies.

Adrienne Jochum and her team investigated the insides of the shells using nanoCT to differentiate species in synchronization with molecular approaches for genetic delimitation. Four well-defined genetic lineages were determined from a total of sixteen Zospeumspecimens found in the type locality region of the most common representative, Zospeum isselianum. This investigation is the first integrative study of live-collected Zospeum cave snails using multiple lines of data (molecular analyses, scanning electron microscopy (SEM), nano-computer tomography (nanoCT), and histology.

This work is dedicated to the industrious Slovenian malacologist Joze Bole, whose work greatly inspired the present research.

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Original source:

Jochum A, Slapnik R, Klussmann-Kolb A, Páll-Gergely B, Kampschulte M, Martels G, Vrabec M, Nesselhauf C, Weigand AM (2015) Groping through the black box of variability: An integrative taxonomic and nomenclatural re-evaluation of Zospeum isselianum Pollonera, 1887 and allied species using new imaging technology (Nano-CT, SEM), conchological, histological and molecular data (Ellobioidea, Carychiidae). Subterranean Biology 16: 123-165. doi: 10.3897/subtbiol.16.5758

New snake species with pitch black eyes from the Andes highlights hidden diversity

Extremely rare and hidden in the forests of the Andes, there are still new snake species left to find. This has recently been evidenced by the colubrid serpent, described for the first time in the present article. Moreover, there is the vicious circle enwrapping its relatives: the harder it is to find more specimens, the tougher it is to describe and thus, start to identify them, which does not help in mapping their distribution and habitats. To address this issue, Dr. R. Alexander Pyron, The George Washington University, and his international research team have included a taxonomic review and discussion on the relationships and origin within a non-venomous snake tribe in a paper, published in the open-access journal ZooKeys.

Slender and small, the new species, called Synophis zaheri, measures less than 40 cm in length, or between 351 and 372 mm. Contrasting to its slim body with a distinct neck, separating the head from the body, its eyes are large and bulging, making up for more than a third of its head. Being black in colour, it is hard to tell the pupil and the iris apart. While the upper part of the body is grayish-brown with an iridescent sheen, the abdominal side stands out with its yellowish-white colouration.

Typically for the tribe, where the new species has been placed, it is also characterised with a highly modified spine and an enlarged scale row running over it. This is also where the name of this group of snakes comes from with “Diaphorolepidini” consisting of the Greek words for “differentiated” and “scales”. Not so clear, however, is the name of the genus, which the authors have translated also from Greek as “with snake”, but find themselves unaware of the meaning behind. The species is named after Dr. Hussam El-Dine Zaher, a Brazilian herpetologist whose work has been foundational for South American snakes.

In conclusion, the scientists note that the rarity of the observed snake species, especially the genus, where the new serpent belongs, accounts for the unclear species-boundaries as well as for the myriad of undescribed species. “Dipsadine diversity in the Andes is clearly underestimated, and new species are still being discovered in the 21st century,” they point out.

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Original source:

Pyron RA, Guayasamin JM, Peñafiel N, Bustamante L, Arteaga A (2015) Systematics of Nothopsini (Serpentes, Dipsadidae), with a new species of Synophis from the Pacific Andean slopes of southwestern Ecuador. ZooKeys 541: 109-147. doi: 10.3897/zookeys.541.6058

Call for arms and stings: Social wasps use alarm pheromones to coordinate their attacks

Humans might know them as vicious stingers, but yellow jacket wasps also impress with their vigorous protection over their young. To resolve the mystery around their complex defensive behavior, a Canadian research team, led by Dr. Sean McCann, Simon Fraser University, have used simple components to develop and construct a device that consequently helped them to locate the species-specific alarm pheromones in three wasp groups. The insects use the emission of these substances to mark the enemy threatening their colonies and then join forces against it. The study is published in the open-access Journal of Hymenoptera Research.

Social insects invest a lot of work and resources in their colonies, working together to raise large numbers of larvae. Because their nests contain so many protein-rich, yet helpless young, they have evolved elaborate defence mechanisms to protect them.

One way the social wasps have found to increase the efficiency of their defence is through chemical signals, called alarm pheromones, which are used to rouse the colony to action and mark intruders for attack. As a result, the coordinated attack of a large colony of yellow jackets can drive even large predators away from the nest. Several social wasp alarm pheromones have been discovered, and most of these have been detected in the venom sacs of the wasps. Nonetheless, the process of finding out which chemicals are involved requires many experiments in the field in addition to chemical analysis.

“We developed a new and standardized method to evaluate alarm pheromone activity in yellowjackets and other social wasps that is inexpensive and easy to use. The device we constructed uses off-the-shelf components, and consists of a pair of black targets enclosing a pair of microphones,” explain the authors.

“A test substance and a control can be applied to each target, and then a stereo audio file is recorded at the nest site,” they further comment. “When wasps hit the black targets, it makes a percussive sound, almost like a drum. The resulting stereo file is then split and analysed with an open-source software program to count the number of strikes received by the treatment and control targets.”

The advantage of this system is its ease of use, low cost, and the ability to use rapid automated counting, which saves a lot of time compared to other methods.

The scientist have used this new method to figure whether three species of yellow jackets (the western yellow jacket, the common yellow jacket and the German yellow jacket) have alarm pheromones, and whether each species is able to recognize each of the alarm pheromones of the rest.

“We found evidence for alarm pheromones in all three species, and that each species recognizes and responds to the other species’ alarm pheromones in similar ways,” say the researchers. “We conclude that the chemical messages produced by these three yellow jacket species must be very similar.”

“It makes sense that wasps can recognize the alarm pheromones of other species, because it would be advantageous to be able to detect a pheromone-marked predator that has attacked other wasps nearby and start stinging it to drive it away before it finds their own colony,” conclude the authors.

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Original source:

McCann S, Moeri O, Jimenez SI, Scott C, Gries G (2015) Developing a paired-target apparatus for quantitative testing of nest defense behavior by vespine wasps in response to con- or heterospecific nest defense pheromones. Journal of Hymenoptera Research 46: 151-163. doi: 10.3897/JHR.46.6585.

Guardian ants: How far does the protection of a plant-ant species to its specific host go?

Seemingly helpless against their much more lively natural enemies, plants have actually come up with a wide range of defences. In the present research, published in the open-access Journal of Hymenoptera Research, Dr. Adriana Sanchez, Universidad del Rosario, Colombia, and Edwin Bellota, Texas A&M University, USA, focus on the mutualistic relationship developed between a specific Neotropical knotweed and an ant species. During a series of ant-exclusion experiments the scientists observed and subsequently reported an aggressive and highly protective behaviour.

In order to assess the extent of protection these plant-ants provide their exclusive host with, the researchers compared the percentage of herbivory between control plants and experimental ones, which had their resident ants removed. The unambiguous results showed a 15-fold increase in the herbivory in the latter group, which kept on growing even further as the time progressed.

Normally, the studied ants patrol their hosts during both day and night at temperatures sometimes as low as 13C. Every time they found a herbivore, they were seen to attack it aggressively by biting and stinging.

“When an ant encountered a caterpillar, a worker approached and detected it with its antennae, and then recruited more workers. Typically more than 10 workers were recruited around the intruder in less than five minutes,” shared their observations the researchers. “Several workers harassed the herbivore by stinging or biting, until it dropped off the plant. The caterpillars usually hung by a silk thread and attempted to move back onto the plant. However, individuals of Pseudomyrmex continued to chase them until they dropped again. This cycle was repeated several times.”

While patrolling, they were noticed to remove any found debris from the top of the leaves. When they failed to find any signs of mosses, fungi or lichens on the sampled saplings, the scientists suggested that the ants not only protect their host from herbivores, but also from various disease-causing agents.

Plant vitality, growth and reproduction are seriously threatened by herbivores such as, in the case of the hereby studied knotweed, Triplaris americana, caterpillars and grasshoppers. Fighting for their life, plants use structural defenses, toxins, digestibility-reducing compounds, or mutualistic relationship with the enemies of their herbivores.

The herein researched Neotropical plant have found its way of survival through becoming the only host to the ant species Pseudomyrmex dendroicus, characterised with remarkable eyes, light brown body and potent venom, injected through a well-developed sting. In its turn, the knotweed shelters their entire colony in its hollow stems while another symbiont, scale insects, feeds them with the sugary sticky liquid it secrets on digesting plant sap.

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Original source:

Sanchez A, Bellota E (2015) Protection against herbivory in the mutualism betweenPseudomyrmex dendroicus (Formicidae) and Triplaris americana(Polygonaceae). Journal of Hymenoptera Research 46: 71-83. doi: 10.3897/JHR.46.5518.

Rare Amazonian butterfly named after British national treasure Sir David Attenborough

A beautiful new Black-eyed Satyr species has become the first butterfly named in honour of the popular naturalist and TV presenter Sir David Attenborough. Although not the first animal to be named after the British national treasure, the butterfly is so rare that it is known only from lowland tropical forests of the upper Amazon basin in Venezuela, Colombia, and Brazil. The study, conducted by an international team of researchers, led by Andrew F. E. Neild, Natural History Museum, London, and Shinichi Nakahara, McGuire Center for Lepidoptera and Biodiversity and Entomology & Nematology Department, University of Florida, is published in the open-access journal ZooKeys.

The presently described Attenborough’s Black-eyed Satyr, scientifically called Euptychia attenboroughi, has such a restricted distribution that all of its known sites lie within 500 kilometres from each other in the north-west of the upper Amazon basin.

Best known for scripting and presenting the BBC Natural History’s ‘Life’ series, Sir David Attenborough is also a multiple winner of the BAFTA award and a president of Butterfly Conservation.

“Other animals and plants have previously been dedicated to Sir David, but it makes us happy and proud to be the first to dedicate a butterfly species in his name,” says Andrew Neild. “Although we are a large team from several countries from across four continents and speaking different languages, we have all been deeply influenced and inspired by Sir David’s fascinating and informative documentaries.”

The butterfly’s atypical wings in comparison to its relatives, have been the reason the scientists took to plenty of diagnostic characters to define its taxonomic placement. The peculiar patterns and morphology initially led the researchers to think the species could be even a new genus.

“It was a surprise for us that DNA data supported inclusion of this new species in the existing genus Euptychia, since this species lacked a distinctive structural character which was considered to be shared by all members of the genus” explains Shinichi Nakahara.

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Original Source:

Neild AFE, Nakahara S, Zacca T, Fratello S, Lamas G, Le Crom J-F, Dolibaina DR, Dias FMS, Casagrande MM, Mielke OHH, Espeland M (2015) Two new species of Euptychia Hübner, 1818 from the upper Amazon basin (Lepidoptera, Nymphalidae, Satyrinae). ZooKeys 541: 87-108. doi: 10.3897/zookeys.541.6297

To kill a wolf spider: Further observation of a spider wasp larva growing on its host

Having been attacked, paralysed and implanted with a wasp egg to its belly, a wolf spider carries on with its life fully mobile and active. At least, until it is time for the larva to reach out for its first solid meal at a certain development stage. The present study, conducted by a Brazilian team of scientists, led by PhD student Hebert da Silva Souza, Universidade Estadual de Campinas, Sao Paulo, and published in the open-access Journal of Hymenoptera Research, follows the entire cycle of larval development from the egg laying through the formation of a full-grown wasp.

The herein observed wasp species, called Paracyphononyx scapulatus, belongs to a well-known group of spider parasites, which after laying their eggs on a paralysed spider, let it recover and continue living fully mobile until the larvae are mature. However, little has been known about this curious behaviour of this wasp species in particular, since previous studies have already showed differences between the separate members of the genus.

To observe the whole cycle of the wasp larval development, the researchers caught a recently parasitised wolf spider and placed it in a plastic container.

While the larva grew and fed on the abdominal hemolymph, which is the analog to the blood in backboned creatures, its host did not show any peculiarities in its behaviour and even kept its routine being active at night and resting during the day. This is suggested to be attributed to the need of the larva to keep its host safe from predators, such as ants, which could otherwise eat the dead body.

However, ahead of its fifth and last development stage, the larva was seen to double its size and, in the morning, twenty days after the hatching of the egg, it killed its host and fully consumed it within the next forty-eight hours. Having left its host, the larva began to search for a place within the container to construct a cocoon, which took it sixteen hours. Thirty-two days later, a fully grown female wasp emerged.

In comparison, a relative of the observed spider wasp is known to manipulate its host’s behaviour, making it to enwrap itself and the larva in a cocoon-like silken structure so that it is protected while feeding. Yet, it is not certain whether the observed larva’s growth in captivity is not the reason why it had not induced similar behaviour.

In conclusion, the authors suggest that further investigation of the interaction between the two species could provide more information about the evolution of this kind of parasitism, which is likely to have developed independently among the wasp groups.

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Original source:

Souza HS, Messas YF, Masago F, dos Santos ED, Vasconcellos-Neto J (2015) Paracyphononyx scapulatus (Hymenoptera, Pompilidae), a koinobiont ectoparasitoid of Trochosa sp. (Araneae, Lycosidae). Journal of Hymenoptera Research 46: 165-172. doi: 10.3897/JHR.46.5833