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3 Posts tagged with the weevil tag
1

The Dark Side of Weevils

Posted by Blaps Jun 9, 2015

Weevil researcher Dr. Chris Lyal elucidates on the darker side of weevil life-histories...they are not as friendly as you may have imagined...

 

 

 

Weevils are perhaps the most inoffensive of beetles - well, unless you’re a farmer, forester or horticulturalist, in which case you may take a rather dimmer view of them, since some species of this huge group are major plant pests.  However, to focus on the animals themselves and ignore inconvenient economics, they seem to look out at the world through immense soulful eyes, and trundle rather erratically along like one of those clockwork plastic children’s toys with slightly more legs than are truly manageable. As herbivores, they spend their lives up to their antennae in plants, nibbling at leaves and flowers, buds and roots.  They may have a long projecting rostrum at the front of their heads, but they do not behave like horse-flies, bed-bugs or any of the rest of the blood-sucking brigade and try and force it through your skin and suck out your life-juices. Adult weevils are covered in scales and sometimes very brightly coloured, but they have a previous existence as a larva, chomping their vegetarian way inside fruit, stems, leaves or roots. Larvae are fat, white, legless comma-shaped beasts, almost blind and apparently interested only in food. Again, not one of nature’s  bad boys (unless, as I said, you are concerned with keeping plants alive, in which case I may be irritating you by now). However, not all is as it seems. Some weevils, it turns out, have a darker side to their nature. Some are killers. Some are cannibals.

 

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Damnux species, a seed predator of dipterocarp trees in Thailand.

 


Our first instance is rather sad, albeit with a shocking element. Most weevil females drill a hole in the host plant using their rostrum – the projection of the front of the head at the end of which is the mouth. They then turn around and carefully lay their egg in the bottom of the hole they have produced. This process, to the observer, can be tense – how does the female know where the hole is? Will she find it, probing blindly with her ovipositor? Not always, it turns out. Several species of European Ceutorhynchine weevils, including the stem cabbage weevil Ceutorhynchus napi, occasionally lay their eggs too soon, and miss their carefully drilled hole. The larva would not survive, were the egg to even hatch. Pragmatically (though not sentimentally – but one can take anthropomorphism too far), rather than waste the resource the female will eat the egg, and therefore be able to use the nutrition to develop more eggs[1] . More deliberate is the elegant Ludovix fasciatus, which lays its eggs in the stems of the water hyacinth, Eichornia crassipes. This is no simple placement in the plant tissue – the female probes with her long slender rostrum until she finds eggs of the grasshopper Cornops, already laid inside the stem. On finding a clutch, she inserts her rostrum into one and, rather like drinking milk from a coconut through a straw, drains the contents. She then lays a single egg and the larva, when it hatches, eats the rest[2] .  Even more extreme is Anthribus nebulosus, another European weevil, which has taken on some of the characteristics of a parasitoid. In this case the female searches out scale insects on coniferous trees, just after the scale produces eggs. The beetle chews a hole in the scale and lays an egg in the ovisac; when the larva hatches it stays where it is, feeding on the scale’s eggs and nymphs before pupating in the same place. When the adults emerge they feed on the remains of the scale, with the occasional pause to imbibe some honeydew as an accompaniment.  Scale insects are not the only Hemiptera to suffer at the mouths of weevils. Researchers in a lab in New Zealand a few years ago, studying resistance of grasses to the pest weevil Listronotus bonariensis, noticed that aphids accidentally included on the grass vanished during the experiments.  Closer examination revealed the adult weevils, if they encountered an aphid as they walked across the plant, would ‘grasp and rupture the aphid with the mandibles, followed by mastication and ingestion’[3]. Nice

 

 

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The larva of a molytine weevil, Alcidodes ramezei, in a dipterocarp seed.
 

The instance that led me to this curculionoid underworld, however, is more extreme, and that was a paper that came out recently on a seed-feeding weevil, with an intriguing title: “Curculio Curculis lupus: biology, behavior and morphology of immatures of the cannibal weevil Anchylorhynchus eriospathae[4] . Many weevils feed on plant seeds as larvae. This is a very good source of food, neatly packaged and concentrated. With one exception, the bizarre cycad-feeding brentid Antliarhinus (of which more, perhaps, another time) generally only one or, more rarely, a few, weevils can develop in a single seed. In fieldwork I sometimes find, on opening a seed, a weevil pupa fully occupying the interior, neatly packaged and waiting to emerge. How weevils arrange this singular occupancy is not clear. In some cases, perhaps, females can detect if another female has already oviposited and avoid the fruit; in others, there may be so many fruit and so few weevils that competition is rare. Perhaps if there is more than one larva there is simply not enough food and one or both starve – so-called ‘scramble competition’.  Maize weevils normally produce several adults from a single seed however many eggs are laid, and aggression between larvae has been seen by X-raying the seed. In the case of two weevils feeding on fruit of the palm Syagrus, however, the mechanism is known, and it’s not pretty. Most weevil larvae have broad triangular mandibles, suitable for chewing plant tissue.

 

 

 

This is the case of the older larvae of weevils in the genera Revena, a baridine, and Anchylorhynchus, a curculionine.  In both cases, however, the first instar larva is different.  The mandibles are long, slender and pointed – predator’s mandibles.  With such mandibles chewing plant material would be difficult, but piercing and killing other insects – that is where one sees this morphology in other beetles. The first intimation of what was happening was in a paper by Cecilia Alves-Kosta and Chrisoph Knogge in 2005[5] , where they discovered the first instar larvae attacked and killed one another, should more than one egg be laid in a fruit. The larva remained in this killer instar until the endocarp of the fruit hardened and no more eggs could be laid, after which it moulted into the more ‘normal’ second instar.  The story was elaborated more recently by Bruno Souza de Medeiros and his colleagues who last year published the paper mentioned above on the ‘weevil wolf’, Anchylorhynchus eriospathae.

 

 

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Anchylorhynchus eriospathae larval mandibles (redrawn from de Medeiros et al, 2014):  first instar, dorsal and ventral.

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Anchylorhynchus eriospathae larval mandibles (redrawn from de Medeiros et al, 2014): 2nd instar, dorsal and ventral.

 

Like Revena, the 2nd, 3rd and 4th instar larvae have blunt triangular mandibles and, like Revena, those of the first instar are long, slender and pointed. In this case the eggs are laid on the flowers before the fruit are formed, and the larvae, flattened and with long setae to detect their competitors and prey, slide between the sepals and petals of the flower and fruit, fighting and killing others they find.

Unlike Revena they then eat them, a so-far unique observation of cannibalism in weevils. Some cases have been seen of more than one later instar in a fruit, but in this case the ignore one another, other than feeding at opposite ends of the fruit in scramble competition to mature earlier than their competitor – other weevil larvae entering the fruit may still be killed, however.  The two beetles showing this amazing development of the first instar are not closely related, and similar adaptations have not been seen elsewhere in seed-feeding weevils (other than in congeneric species on the same hosts).  On the other hand, not many people have looked.  In fact, we apparently need to look even more widely. Since I wrote the text above another paper has revealed intraspecific aggression in weevils with a totally different lifestyle, where the larvae live externally on the plant – members of the subfamily Hyperinae. Jiří Skuhrovec and his colleagues found that fighting to the death can occur in cultures of two different hyperfine species, Hypera postica and Brachypera vidua[6]. In this case there does not seem to be cannibalism or modification of the mouthparts (although they have introduced some wonderful terms: ‘offensive larva’, ‘defensive larva’ and ‘combat ball’).

What would lead to the evolution of the behaviour and morphology in these weevils, especially those attacking the Syagrus seeds? The leaf-feeding Hyperinae only demonstrate the behaviour when there is insufficient food.  For the seed-feeders one perhaps critical factor is the very high seed-predator load of the plant; it is not unusual for 100% of the seeds to be attacked. This would lead to intense competition, driving the weevils to develop means of eliminating other larvae competing for the same resource – and maybe obtain some extra nutrient at the same time.  One thing is clear – there can be only one.   

 

 

[1] Kozlowski, M.W., 2003, Consumption of own eggs by curculionid females (Coleoptera: Curculionidae: Curculioninae, Ceutorhynchinae) – Weevil News: http://www.curci.de, No.10, 4pp., CURCULIO-Institut: Mönchengladbach (ISSN 1615-3472). http://www.curci.de/weevilnews/no/10/

[2] Zwolfer, H. & Bennett, F.D., 1969, Ludovix fasciatus Gyll. (Col., Curculioninae), an entomophagous weevil. Entomologists Monthly Magazine, 105: 122-123

[3] Barker, G.M., 2006, Predation on aphids by the herbivorous weevil Listronotus bonariensis (Kuschel) (Coleoptera: Curculionidae: Brachyceridae).  The Coleopterists Bulletin, 60(2), 164-165.

[4] de Medeiros et al. (2014), Curculio Curculis lupus: biology, behavior and morphology of immatures of the

cannibal weevil Anchylorhynchus eriospathae G. G. Bondar, 1943. PeerJ 2:e502; DOI 10.7717/peerj.502

[5 Alves-Costa CP, Knogge C. 2005. Larval competition in weevils Revena rubiginosa (Coleoptera:

Curculionidae) preying on seeds of the palm Syagrus romanzoffiana (Arecaceae).

Naturwissenschaften 92:265–268 DOI 10.1007/s00114-005-0620-6.

[6] Jiří Skuhrovec, Pavel Štys & Alice Exnerová (2015) Intraspecific larval aggression in two species of Hyperini (Coleoptera: Curculionidae), Journal of Natural History, 49:19-20, 1131-1146, DOI: 10.1080/00222933.2014.974704

2

Chris Lyal and Conrad Gillett last left us as they were returning to Beijing after a fortnight of weevil collecting in southern Yunnan. The final part of their blog details the last few days of their trip during which they were hosted by colleagues of the Institute of Zoology (IoZ) at the Chinese Academy of Sciences (CAS) in Beijing.

 

"After our collecting in tropical Yunnan, we arrived to a Beijing where spring had clearly sprung compared to the wintery scene we had left behind two weeks previously. The campus of the Academy of Sciences now looked decidedly green and flowery. We arrived in the evening and were quite tired from the journey and just wanted to get a good night's rest before a day in the collection the following day. We checked ourselves into the on-campus guesthouse, and managed to communicate with the lady at reception through her ingenious use of an online translation website - isn't technology sometimes wonderful!

 

After a good rest, the following morning we met up again with some of the entomologists at the Institute of Zoology. We were very hospitably looked after by Prof. Runzhi Zhang who is the principal investigator in the Group of Identification & Management of Invasive Alien Species. His colleagues Ren Li and Zhilian Zhang were also of great assistance during our stay.

 

The first thing to do was to sort, store and pack the weevils we had collected over the last two weeks. It is always interesting looking over the specimens again, as inevitably by the time a collecting trip is over, one has a faded memory of some of the early captures! The specimens were moved into fresh ethanol and all were carefully labelled and packed for the voyage home. We had a go at identifying some of the specimens, the Molytinae in particular, through comparison with preserved specimens in the  IoZ collections, although with the limited amount of time we had, this proved a little frustrating and we ended up discovering a whole hoard of additional unidentified weevils as a result of our attempts! Chris’s bright idea of “a short paper covering the Mecysolobini of China since we caught a fair number and there are only 8 species here” was slightly dented by his discovery of 40 distinct unidentified species in the collections. The taxonomist's work is never done!"

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Chris boards our flight back to Beijing at Kunming airport, after the small debacle with his cabin bag detailed in part 2 of this blog!

 

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The Institute of Zoology in Beijing - as can be seen, it is a very extensive and modern facility
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Conrad and Chris sorting, labelling and packing specimens

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Some of our catch

 

" The IoZ collections are housed in very good conditions, in a climate-controlled modern room. The specimens are arranged in wooden drawers kept in metal cabinets that are in compactor racks. It all seemed quite well organised. There was a large amount of interesting 'accessions' material which contained lots of weevils that had been identified to tribal level by Miguel Alonso-Zarazaga the previous year, and rather more that he had not managed to get to.

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The modern collection facilities at the IoZ, with metal cabinets in compactor racking

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Chris and Ren Li studying weevils form the accessions material in the collections

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The wooden drawers are housed in the metal cabinets


Did our colleagues get a chance to see anything of Beijing during their visit?

 

"We decided to take part of our last weekend in China off, having been on the go continuously for more than two weeks. One sight that we were both keen to see was the Great Wall of China and on Saturday morning we were very kindly taken there by three of the students in the department who were excellent guides (and translators!). We really would have struggled to make it there on our own as we were not keen on joining a big tourist guided tour. We were able to travel to a section of wall that remains mostly in its original state, which was  preferable to the more easily reached sections that have been rebuilt. Our trip took place on a very misty Saturday, which whilst not being ideal for long uninterrupted views over the length of the wall's winding course, did impart somewhat of a mystical air to proceedings!

 

We eschewed the luxury of a cable car from the starting point  to the Wall itself – had the mist been less we might have reconsidered this, but what turned out to be 1,400 steps later we made it to the top, and were able to explore more than two kilometres of the Wall itself .it must be said that after spending a few hours walking and climbing along the impressive structure (and then descending the 1,400 steps again) we were mostly pretty well spent! We both would like to thank Yang Ni, Zhang Jingjie and Xie Quanrong for a memorable visit to The Wall. And before you think to ask - yes we did find a beetle on The Wall (actually on Chris’s back)- what a great data label that will have!"

 

great_wall.jpgThe Great Wall

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Our lovely guides, left to right: Xie Quanrong,  Zhang Jingjie,  and Yang Ni who took us to and showed us around The Wall

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Chris and Conrad on The Wall

 

"On the following day, Conrad decided to see a few more sights in Beijing, including Tiananmen Square and the Forbidden City. He eschewed the (cheap) taxis for a trip on the Beijing underground system which was very modern and efficient, in addition to being air conditioned and very easy to navigate for a non-Chinese speaker/reader - and all this for 20p per journey! For the equivalent of the London underground tube ticket prices, Conrad could probably have travelled by private helicopter around the city!"

 

"The Forbidden City, the former palaces of the Chinese Emperors, was a stupendous sight - it is absolutely enormous, seemingly expanding wider the further you walk through it! Even after more than two hours , Conrad did not reach the end before having to turn back to head to the final stop on his self-made tour. This was to be the Military Museum of the Chinese People's Revolution as he has a penchant for the 'taxonomy' of military aircraft, and was pleased to be able to see some cold war era hardware, including a good number of fighter jets now peacefully gathering dust in their final resting places.

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One entrance to the Forbidden City at Tiananmen Square - somewhat overshadowed by the acrobatic antics of the chap behind me!

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Inside the (no longer) Forbidden City

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Shenyang J-6 fighter gathering dust at the Military Museum

 

After the weekend it was back to work in the collections for a couple of days before returning to England. Chris met with the director of the IoZ to discuss future possible collaboration with the museum and discovered that the director has links with the UK because he spent time at the University of East Anglia, where both Conrad and one of Chris' daughters also study/have studied!

 

Runzhi Zhang also showed us around a laboratory and quarantine facility just outside Beijing which is used for pest-control research. The labs were very modern and equipped with very similar or identical equipment to what we have back home and is especially well set up for molecular genetics work. We were impressed not only by the modern PCR machines, gel-imaging cameras and freezers, but also by the cute pipette-tip bin! The facilities also included a large number of greenhouses where quarantine of pest interceptions can be undertaken.

 

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Chris and Runzhi Zhang inspect the molecular laboratory in the pest and quarantine facility we visited - the cute pipette-tip bin is a nice touch!

 

"The Institute of Zoology has its very own Natural History Museum and we were able to make a short visit towards the end of our stay. The public galleries contained many well presented and labelled specimens and were very well maintained - it was impressive to see quite so many biological samples on show, mostly exhibiting the Chinese fauna. Insects were very well represented with a separate section for butterflies and one for beetles too - that is not common these days! Over the entrance to the beetle displays, a mammoth-sized bronze rhino beetle (Allomyrina dichotoma) was placed to welcome the visitor. Chris was particularly taken with the display of Zoraptera – possibly the only one in the World - which comprised a two-millimetre specimen inside a plastic vial positioned centrally in a large and otherwise empty case.  Once inside, representatives of many beetle families were found in the wall-mounted displays, all neatly mounted and labelled.

 

However, even for both of us with decades-worth of beetle obsession behind us , it can hardly be denied that the most exciting, entertaining and bewildering exhibition was that in one of the temporary galleries. This gallery was presently in use housing the entries for an amateur taxidermy competition.  That is something that you will not see every day! Although of course taxidermy has played an undeniably important role in natural history museum collections. The entries were remarkable and ranged from those portraying, in almost life-like realism, re-enactments of nature (with a definite bias towards fierce predators mauling their prey) to those that simply defy explanation, representing animals in decidedly unnatural poses, situations and even attire!"

 

 

 

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The Institute of Zoology's very own Natural History Museum

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A giant rhinoceros beetle guarding over the beetle collection!
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A display on insect collecting, complete with net, collecting tubes, pitfall cups, setting boards and other entomological paraphernalia

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A highly dramatic and realistic taxidermy display of wolves hunting an ibex

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An equally dramatic but not-so realistic entry in the taxidermy competition.  Readers who are able to explain anything in this picture are urged to write in

 

"Before we returned to England, we were to experience one last culinary delight courtesy of our ever-charming colleague Ren Li, who very kindly took us out to lunch on our last day in Beijing to experience a gastronomic speciality of Hubei province: donkey. We were taken to a restaurant that specialised in equine epicurean delights such as donkey-skin soup, donkey kebabs (sort of) and donkey hot-pot! It was mostly very tasty but Conrad did struggle with the soup!

 

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Ren Li at a table covered in donkey-based dishes - we thank her for her generous hospitality and for widening our horizons!

 

"And so, having added the last species to our 'eaten it' list, and packed our specimens for travel we bid farewell to all our friends at the IoZ and set off on our long journey home after experiencing a unique country and culture.

We would like to especially thank Runzhi Zhang, Ren Li, Zhilian Zhang as well as all the other people that helped us during our visit to China and without whom it would have been an impossibility. We now look forward to studying the specimens that we collected and hope that they will advance our knowledge of the systematics of that most diverse group of insects, the weevils.

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Conrad

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Chris

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Weevil
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Panda

 

Photographs by Conrad Gillett, Chris Lyal and Ren Li

0

New Years (beetles) Honours list

Posted by Blaps Jan 9, 2011

A belated Happy New Year!

 

With the passing of 2010, we look back over what has been an eventful and at times poignant year for the beetling community. It would be impossible to include everything that happened in and around the Coleoptera department in 2010 in a mere blog, so apologies if anything significant has been missed, but here are a few shining examples to set the standard for the coming year:

 

This year saw two majorly significant collections come to the Natural History Museum, the Vorisek collection of Weevils (Curculionidae) (which is now housed in the Coleoptera department) and AA Allen’s collection of British beetles (which is awaiting deposit to the Museum). These two collections constitute a lifetime’s work of these great Coleopterists and the Museum, indeed the scientific community is indebted to their dedicated work of the previous century.

 

AA Allen

Mr Anthony Adrian Allen (1913-2010) was a leading authority on the British beetle fauna and published hundreds of papers and scientific notes, in a career going back to the 1930s. He formed a bridge between the contemporary community and some of the great names of the past, such as his close contacts Phillip Harwood and Horace Donisthorpe. (Max Barclay, The Coleopterist)

 

This year we intend to digitally scan the whole collection which includes most representatives of all the c.4000 British species, which will then be made available on the internet as a scientific resource, and as a permanent record of A.A. Allen’s immense contribution to the understanding of the British Coleoptera.

 

A.A. Allen’s portfolio of publications included the descriptions of four valid new species of British beetle:

Aleochara phycophila Allen, 1937 (Staphylinidae)

Acrotona benicki (Allen, 1940) (Staphylinidae)

Scraptia testacea Allen, 1940 (Scraptiidae)

Longitarsus fowleri Allen, 1967 (Chrysomelidae)

 

A tribute to AA Allen can be found in The Coleopterist, the journal for British Coleoptera http://www.coleopterist.org.uk/

 

Oldrich Vorišek

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© Libby Livermore 2010

 

Oldrich Voríšek, an amateur Czech collector whose collecting efforts of over 40 years yielded a collection of 45,000 specimens and 4,500 species of weevil from Europe, came to the Museum in 2010. It still takes my breath away to think of it, let alone to even physically start working with the collection. Currently we have a few volunteers, namely Libby and Katie who are assisting in recurating the beetles, and incorporating them into the Museums’ collection. There are 750 Type specimens which through our curating efforts will eventually be made widely available to the scientific community, both physically and virtually!

 

For more information on the Vorišek collection follow this link.

http://www.nhm.ac.uk/about-us/news/2010/august/wonderful-weevil-collection-comes-to-museum79149.html

 

 

New species

 

And now to the lighter side of the news, new species are discovered and described every year by the academic Coleoptera community, and in this age of decreasing biodiversity (of named species), it is ever more important to know what we have got. My vote for new species of the year goes to Hydroscapha redfordi (10 of the type series are deposited here in the Natural history Museum).

For a full description here is the paper citation:

Crystal A. Maier (a), Michael A. Ivie (a), James B. Johnson (b) and David R. Maddison (c). 2010. A New Northern-Most Record for the Family Hydroscaphidae (Coleoptera: Myxophaga), with Description of a New Nearctic Species. The Coleopterists Bulletin

http://www.bioone.org/doi/full/10.1649/0010-065X-64.4.289

 

The authors’ decision to name the species after the great actor, director and environmental campaigner Robert Redford, for his continued efforts to support the conservation of the Rocky Mountains, is prompted by the film Jeremiah Johnson, with Redford playing the leading role. Hydroscapha redfordi is found in hot springs where it inhabits rock faces covered by mats of filamentous algae. The Type locality of this species is Jerry Johnson Hot Springs.

Here is Robert Redford with an animal at least beginning with ‘B’, if not an actual beetle!

 

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Image Courtesy of IMDB

 

New species are often named in honour of significant people (known as patronyms), either in the scientific community, for example the Lucanid, (Scarabaeoidea) Erichius darwinii Paulsen 2010, another new species for 2010, or in the world of popular culture, such as Agra katewinsletae (Carabidae) Erwin, 2002. You might have guessed, after the actress Kate Winslet for her role in Titanic. In the original description Erwin cites his somewhat tenuous choice of name, Her character did not go down with the ship, but we will not be able to say the same for this elegant canopy species, if all the rain forest is converted to pastures. Well said!

 

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Some specimens of the curious aboreal carabid, Agra.

 

And to end on a tragi-romantic note, here is Kate and Leo...you know what happens next...

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Next week, fieldwork from 2010...



Blaps

Blaps

Member since: Sep 15, 2009

I'm Beulah Garner, one of the curators of Coleoptera in the Entomology department. The Museum's collection of beetles is housed in 22,000 drawers, holding approximately 9,000,000 specimens. This little collection keeps us quite busy!

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