Caterpillar defense against beetles

This video says about itself:

Watch this caterpillar fling its beetle attacker through the air

23 February 2018

Hornworm moth larvae have several tricks to defend themselves against predators. Learn more here. And here.


Australian fire beetles avoid heat

This 13 february 2018 video is called The impact of infrared radiation in flight control in the Australian “fire beetle” Merimna atrata.

From the University of Bonn in Germany:

Australian fire beetle avoids the heat: Its infrared organs warn the insect of hot surfaces

February 15, 2018

Summary: The Australian jewel beetle Merimna atrata has several heat sensors. Originally it was thought that it uses them to detect forest fires as the insect lays its eggs in the wood of burned eucalyptus trees. Researchers were finally able to refute this hypothesis. Instead, the beetle appears to need its heat sensors for a different purpose: to not burn its feet on landing.

The Australian fire beetle is attracted to freshly burnt wood. Experts also call this pyrophilia (“love of fire”). This behavior is not very common in insects. Merimna atrata however has a good reason for this. The dead wood provides plenty of food for the larvae of the beetle, so it uses the wood for oviposition.

But how does Merimna find a freshly burned area? For some time it has been known that the fire beetle has heat sensors with which it can detect infrared radiation. In a sense, it “sees” hot places in its environment against a cooler background. It was originally believed that the insects use this ability to detect forest fires.

“However, the IR organs in Merimna atrata are relatively insensitive,” Dr. Helmut Schmitz emphasizes. Schmitz is a lecturer at the Institute of Zoology at the University of Bonn; he has investigated thermo and infrared reception in the black insects for nearly two decades. “This actually contradicts the assumption that the IR organs enable the beetle to detect fires from a greater distance.”

Beetles on a pin

Together with his colleagues, Schmitz has now been able to demonstrate for the first time that these doubts are justified. The scientists designed an ingenious experiment for this purpose. Put simply, they stuck the beetles with their backs to the end of a pin and used this to hang them up. This left the experimental animals with the ability to fly continuously, but without moving forward. “More importantly, they were able to navigate in any direction, i.e. turning right or left,” emphasizes Schmitz.

Then the scientists stimulated the flying beetles with weak infrared radiation from the side. The beetles changed their flight direction in response, but always away from the source and never towards it.

“Merimna’s IR organs are located on both sides of its abdomen; incidentally, this is unique in the animal kingdom,” explains Schmitz. “When we occluded the IR receptors with aluminum foil, the animals no longer reacted to the radiation, but always carried on flying straight ahead. As soon as we removed the foil they displayed their original behavior again.” This observation suggests another use of the heat sensors. “Presumably they help the fire beetles avoid hot spots when approaching an oviposition site such as a freshly burnt branch; these hot spots are not visible with the naked eye to humans and animals during the day,” says Schmitz.

How the animals detect forest fires remains unclear. Even visual stimuli seem to play no role in fire detection, despite Merimna atrata having good eyesight. The researchers tested this hypothesis by showing the beetles slides of large clouds of smoke rising above a forest area. But the insects were completely unimpressed and they never changed their flight direction.

Following their nose

“We therefore assume that Merimna atrata gets its information about an ongoing fire from the smell of smoke,” concludes Helmut Schmitz. This is also important for another reason. Odors can tell you exactly what is actually burning. In contrast, this information cannot be inferred from the heat development or the appearance of a smoke plume. Merimna is very picky, it only lays its eggs in burnt eucalyptus wood and avoids other trees. If the insect was to rely on its IR sense, it would risk being lured into the wrong kind of fires.

Something quite different can be seen with a close European relative; the fire beetles of the genus Melanophila. Their larvae develop in a variety of trees. Heat perception would be quite worthwhile for them. In fact, Melanophila also has infrared sensors, but they are completely different. They can presumably detect infrared radiation even from a long distance. According to measurements and theoretical calculations, Melanophila heat sensors are at least 500 times more sensitive than those of Merimna atrata.

Australian beetles’ colours, new study

This video from Australia says about itself:

25 February 2017

A slideshow of leaf beetles in the genus Paropsisterna.

From the Yale-NUS College in Singapore:

Beetles’ bright colors used for camouflage instead of warning off predators

First study to examine beetle colouration in their natural habitat prompts discovery

December 4, 2017

NUS College Postdoctoral Fellow Eunice Tan has discovered that the bright colour patterns of beetles are not a warning signal to predators as previously believed, but actually a form of camouflage, turning an old assumption on its head. Dr Tan, along with four collaborators from Australia and Spain, examined 51 species of Australian leaf beetles in their natural habitats, and discovered that each beetle’s colour pattern is similar to the host plants that the beetle lives on, suggesting that those conspicuous colours help the beetle blend in with the plants it inhabits. The study was recently published as an open-access article in the peer-reviewed journal Frontiers in Ecology and Evolution.

As the first ecologist to examine the colour patterns of live leaf beetles in relation to their host plants, Dr Tan contextualised the colour patterns of beetles to their natural habitats, which allowed her to challenge the prevailing theory among coleopterists — scientists who study beetles — that the bright colours of leaf beetles developed as a deterrent signal to predators. These colourful markings were assumed to be a warning to predators against eating the beetles, which are able to secrete poisonous chemicals in self-defence. However, this idea was based on earlier studies, which focused on using museum collections of beetle specimens for their analyses. While this method affords researchers a large number of samples, the discolouration of deceased specimens made accurate colour analysis of the beetles impossible. Furthermore, such methodology also fails to take into account the colouration of each beetle’s natural environment.

Dr Tan and her team spent 17 months photographing live beetles in 32 locations across four Australian states, in order to compare each beetle’s colouration to the colour of the leaf it was found on. Taking into account the evolutionary relationship between the different beetle species, Dr Tan discovered that different species of beetles had colour patterns similar to those of their host plants. This suggests that the colourations have a camouflaging effect, rather than serving an aposematic (predator-deterring) function. This camouflage effect was particularly pronounced in beetles which fed on multiple types of plants, as they had to blend into many different environments.

“It was long thought that conspicuous colour patterns served to advertise the distastefulness of an organism to its predators. However, we have found that this cannot be the sole reason that conspicuous colour patterns developed in leaf beetles. In general, the beetles had colouration similar to that of their host plants, suggesting that there is natural selection at play and therefore some evolutionary advantage for these beetles to use camouflage as a defensive strategy against predators,” shared Dr Tan.

Through her field studies, Dr Tan also observed the impact of ecological factors on the evolution of different beetle species’ colouration patterns. Dr Tan’s study found that both larger and smaller beetle species in her sample had similar levels of colour contrast against their backgrounds. However, the larger beetle species were more likely to be found in darker environments than their smaller cousins, suggesting that they were employing a hiding strategy against predators, despite having similar conspicuous colouration to their smaller cousins. An ecological property, the brightness of the environment, was therefore a potential factor influencing the evolution of beetle colouration.

Taken together, the findings of this study “point to a complex suite of factors driving natural selection, such as types of predators and host plant choice, which affect the evolution of colouration in leaf beetles,” said Dr Tan. Challenging the assumption that the sole explanation for bright coloration in leaf beetles is meant to ward off predators, Dr Tan postulated that the variety of anti-predator strategies in leaf beetles that she has found may explain their successful spread into a variety of habitats.

New beetles discovered in Borneo

This video says about itself:

A documentary exploring the diversity and conservation of one of the world’s last remaining true wildernesses, Maliau Basin in Borneo. Filmed Jan – March 2016 by Matt Jarvis.

Recently, there was an expedition by Naturalis museum in the Netherlands to the Maliau Basin in Sarawak in Malaysia, on Borneo island. They discovered five beetle species, new for science.

Probably, they discovered many more species new for science. However, the scientists in the expedition were specialists of some beetle families and did not know everything on other beetles and animals. So, further research on what they found may discover much more.

An extensive web site, in Dutch, about the expedition is here.

American oil beetles video

This video from the USA says about itself:

American Oil Beetles – Blister Beetles

14 October 2017

Do not ever touch these beetles! Bizarre bugs indeed! I happened upon about a dozen of these beauties in a fall mating frenzy centered around two very large females full of eggs.

Fortunately I did not step on them in the middle of the trail. They are called Blister Beetles because they emit an oil that will burn the skin if you pick them up. The poison they contain is among the strongest known. Cantharidin is an odorless, colorless fatty substance of the terpenoid class, which is secreted by many species of blister beetles. It is a burn agent or a poison in large doses, but preparations containing it were historically used as aphrodisiacs. In its natural form, cantharidin is secreted by the male blister beetle and given to the female as a copulatory gift during mating. Afterwards, the female beetle covers her eggs with it as a defense against predators.

Research has illuminated the piecemeal patterns of recolonization among a hardy species of beetle regularly affected by managed burns: here.

Brazilian beetles threatened by climate change

This 2014 video says about itself:

Macraspis bivittata (Scarabaeidae – Rutelinae – Rutelini) scarabs or scarab beetles, Santo Amaro da Imperatriz, Santa Catarina, Brazil.

From the University of York in England:

Tropical beetles face extinction threat

October 17, 2017

Climate change is putting many tropical high altitude beetles at risk of extinction, warn an international team of scientists.

Research by the University of York, the Federal University of Rio de Janeiro (UFRJ) and the Federal University of Goiás has found that two plant-eating beetle groups — weevils and leaf beetles — are particularly vulnerable to climate change.

The researchers surveyed a number of insect groups at different altitudes in the Brazilian Atlantic Rainforest, an area known for its high diversity of plant and animal species.

They found that a large proportion of species, mostly from the diverse herbivorous beetle groups, are only found at higher altitude. This puts these species at high risk of extinction as they have nowhere to go when the climate gets warmer.

Dr Peter Mayhew, of the University of York’s Department of Biology, one of the investigators, said: “Previous research has shown that species are moving uphill as the climate warms and that tropical mountain species may be particularly vulnerable because they will become restricted to smaller and smaller areas in a warming planet.

“Our study showed that the most diverse herbivorous beetle groups — the weevils and leaf beetles — are highly specialised to high altitudes, which means their favoured temperatures may disappear in a warmer world. This puts them at high risk of extinction.”

The study was carried out in the Serra dos Órgãos National Park in the state of Rio de Janeiro in Brazil and the results published in the journal Insect Conservation and Diversity.

Insects make up the most diverse group of species in rainforests, but until now little was known about how various insects might be affected by climate change.

Professor Margarete Macedo, one of the research leaders at the Federal University of Rio de Janeiro (UFRJ), said: “Almost nothing is known about elevational specialisation in tropical rainforest insects and our aim was to see how different insect groups varied. This in turn may indicate their risk of extinction from climate change.”

The researchers sampled 697 species of insects, using many different trapping techniques such as sticky traps, pitfall traps and tent-like ‘Malaise’ traps. They discovered that 32 per cent of the species sampled were only found in the highest vegetation zones.

Dr Vivian Flinte, from UFRJ, did much of the collecting, sorting and identification. She said: “It has been a huge team effort over many years to get the data we have now, but we have only just skimmed the surface of what is out there.”

Dr Mayhew added: “Even though the area we studied is in a national park, the species in it are not protected from climate change. Because most of these species are poorly known, their extinction may largely go undocumented, but we will have lost them nonetheless. It makes it all the more important to limit future climate change as much as possible.”

New diving beetle species discovered

The two beetle species

This picture shows the two species which scientists have shown are genetically divergent, Meladema coriacea (left) and Meladema lepidoptera (right). Credit: David Bilton – University of Plymouth.

From the University of Plymouth in England:

‘Hiding in plain sight:’ Discovery raises questions over scale of overlooked biodiversity

October 17, 2017

Scientists have used cutting-edge DNA technology and museum samples collected over the past two centuries to reveal a new species of diving beetle living in streams around the Mediterranean.

Meladema coriacea is among Europe’s largest water beetles and has been considered common across the south of the continent and in North Africa since the early 19th century.

But academics from the University of Plymouth and the Institute of Evolutionary Biology in Barcelona have now shown what was long thought to be one common species is actually two.

Using DNA sequence data and detailed analysis of morphology, they have described a new species — Meladema lepidoptera — which appears virtually identical to Meladema coriacea at first glance, but is very divergent genetically.

Meladema lepidoptera is restricted to Corsica, Sardinia, adjacent small islands and some areas of the Italian mainland, where it apparently occurs to the exclusion of Meladema coriacea.

David Bilton, Professor of Aquatic Biology at the University of Plymouth, led the study having first collected samples of the beetles in the late 1990s.

He said: “We began studying the genetics of these beetles to try to understand how animals had colonised islands — we certainly weren’t looking for, or expecting, a new species. Meladema are some of the largest and best-known water beetles in Europe, so we were very surprised with the genetic results suggesting that there were two species hiding under what everyone thought was only one.”

The new species was in fact ‘hiding in plain sight’, since a study of material from a number of European museums revealed specimens of the newly identified species had been collected as long ago as the mid-19th century. But without the genetic data, these had all been thought to belong to the one, common, species.

Genetic data on more specimens, and a careful study of the appearance of the beetles themselves, has now allowed scientists to identify subtle, but consistent, ways in which the two species differ. This includes the precise sculpturing of their wing cases, with lepidoptera’s appearing rather like the interlocking scales on a butterfly’s wing, hence its name.

Dating based on the DNA analyses suggests that Meladema originated approximately 14.4 million years ago, and that the current species appeared more recently, separating around 1.5 million years ago, perhaps as a result of climate and sea level changes during ice ages.

Professor Bilton added: “This is only one new species, but it’s been hiding amongst one of the largest, most obvious freshwater species in Europe, in an area we have supposedly explored pretty thoroughly. The fact that discoveries like ours are still possible emphasizes how little we know about the biodiversity of this planet, something which should be a major priority, particularly when so much of it is threatened by human activity. To effectively conserve biodiversity, we need to understand what’s out there, because ignorance can lead to the wrong decisions being made about species and habitats.”