Tag Archives: Coleoptera

The Black Oil Beetle

With their slow movements, distended abdomens and their propensity for grass, oil beetles will forgive me for thinking that they are the insect equivalent of cows. Indeed for the short period that this specimen was kept in a pill bottle, it managed to eject a green liquid mass of partially digested plant bits (out of which end I did not observe) that would best be described as cud. But there is a more fascinating side to these grass-grazing beetles that belies their placid and lumbering bovinity — they secrete poison from the leg joints, the males have grappling hooks on the antennae, and the children are ruthless killers.

"The Black Oil Beetle, Meloe niger - Grasslands Provincial Park, Saskatchewan."

So bovinely sleek – The Black Oil Beetle,  Meloe niger

Oil beetles are so named because, when physically disturbed, they exude oily droplets of hemolymph from their joints. This secretion contains cantharidin, a poisonous chemical  that can cause a painful blistering (hence sometimes called ‘blister beetles’) on the skin. Certainly a handy defence when you are a fat, flightless beetle.

The lifecycle is an example of hypermetamorphosis, a variety of complete metamorphosis (holometabolism) with several distinct larval stages. After hatching, the larvae, called triungulinsactively climb plants to seek out a flower, where they will transfer to visiting bees. In Meloe franciscanus, the bees will cluster on a stem and secrete pheromones that attract male ground bees.  When the male tries to mate with the cluster, the triungulins scramble aboard. The male then moves on to mate with other real  female bees, and the triungulins can then transfer to those females. Now fertilized and loaded with larvae, she will carry the triungulins back to the nest, where the little blighters†, going through four instars, will proceed to consume the complete contents of the cell that she constructs and provisions, including the larvae. See the segment from Life in the Undergrowth below for the details of how some blister beetle triungulins  do their work. (This is probably Meloe franciscanus: see http://www.pnas.org/content/103/38/14039.full)

And the grappling-hook antennae? Male oil beetles use the hooks on the antennae to latch onto the females antennae during courtship. See an image of the antennae in use at BugGuide.

"Oil beetle, male antenna hook"

Oil beetle, male antennal hook

And don’t you think this would be a good choice for Alberta’s Provincial Beetle? ;)

For more on oil beetles see page 19 of: Alkali Bees. Their Biology and Management for Alfalfa Seed Production in the Pacific Northwest

Thanks to BugGuide for the ID

(Photographed 25 May, 2012. Grasslands National Park, Saskatchewan)

†Not an entomological term, although it should be…

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Posted in Attenborough, Behaviour, Canada, Coleoptera, Insect, Meloidae, National Park, Phoresy, Saskatchewan, Season, Spring, White Studio | Also tagged , , , , , , , , , 2 Comments

Up to her elbows in dung….

This is a showreel produced for Sarah Beynon, an Oxford entomologist. She’s into dung beetles, but there is also some interesting footage of the Sexton Beetle (see my photograph) and its breeding habits.

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Invader Carabid!

My first outdoor bug shot (in the white box) for 2012! This purple-rimmed Carabus (Carabus nemoralis  Muller, 1764) is also known as the European Ground Beetle.

"Carabus nemoralis, Purple rimmed carabus"

"Carabus nemoralis, Purple rimmed carabus"The elytra on this one was a dull bronze, an unusual sight for me, because I have only seen black specimens before. I noticed it was different immediately as it scurried out of the leaves I was raking in the front garden. The purple-rimmed carabus is a European import that is synanthropic, and not found in the wild.The Edmonton area seems to be an island in Alberta for this species, with only a few having been found outside of the city environs. They are a generalist feeder, taking slugs, snails, earthworms, as well as centipedes and millipedes. Reaching a size between 22 – 26mm, this is a good-sized ground beetle, capable of giving you a nip if handled incorrectly!

 

References

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Posted in Alberta, Canada, Carabidae, Coleoptera, Edmonton, macro | Also tagged , , , , , , , 1 Comment

Stag-jawed Carabid

This is the subject that epitomized my frustrations with my 180mm macro lens! The stag-jawed carabid is a fairly large beetle (25mm/1″) and trying to photograph it with the white-bowl technique with a long-focus macro lens and a single diffused flash was the height of frustration. This is the best front view to come out of the series, but the glare is terrible. This would have been a better candidate for the white-box treatment and a shorter macro lens, but I was in the field and had no other options at the time.

"Pasimachus elongatus, Purple-rimmed Carabid or Stag-jawed Carabid"

 

Pasimachus elongatus LeConte 1846 is a predatory ground beetle that is sometimes mistaken for a stag beetle, which are not found in Alberta at all. They can be distinguished from stag beetles in that the antenna have no elbow and there is no comb-like club at the end. They have a two-year life cycle, overwintering as adults or larvae. They are found…well, let John Acorn take over at this point: “To find this mean-looking, purple-trimmed marvel, go to a patch of bald-butt prairie where the soil is sandy. Then start looking under old fence posts or dried cow pies“¹. I found this one last September in Writing-on-Stone Provincial Park, scampering through the butt-bald badlands.

(Image re-edited 2 April, 2012)

¹Bugs of Alberta by John Acorn and illustrated by Ian Sheldon
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Posted in Alberta, Carabidae, Equipment, Lenses, macro, Provincial Park, Summer, White Studio | Also tagged , , , , , , , 4 Comments

Super Pupa.

"Zophobas morio, the" Superworm" beetle pupa"

A pupa of the ‘Superworm’ beetle, Zophobas morio – a Darkling beetle of the Tenebrionidae family.

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Schtinky Beetle

OK, its not Nicrophorus ‘schtinkii’, but rather Nicrophorus investigator. However, in the confines of my white bowl field studio, and perhaps magnified by parabolic reflection, this burying beetle was more than a little on the stinky side of odoriferous. But then, what else can you expect from a beetle that thrives in rotting flesh?

"Burying beetle, Nicrophorus investigator"

This one was perambulating (‘investigatoring‘?) across a path near the shores of the Milk River in southern Alberta, and I gently guided it into a plastic pill container (8 for a dollar, small and handy, I try to have a few in my pockets at all times) and took it back to camp. I gave it the white bowl treatment for these photographs, which show a few key points about Family Silphidae and the Nicrophorus genus. Working from left to right we see an exposed tushie  abdomen with 3 segments visible behind the elytra, which are short, truncate and black marked with orange. There is dense metasternal  pubescence.  The antenna have a club consisting of four segments, and in N. investigator the basal segment is black with the three apical segments orange. The life cycle of burying beetles is fascinating and I will go into that in a future post. For now I just want to point out the mite that is clinging under the head.

"mite on Nicrophorus invstigator"

This specimen had only one hanger-on, but they can often be found with a great deal more. The mites are phoretic, that is, they are only around for the ride. The burying beetles transport the mites to carrion, and the mites feed on the eggs and grubs that are already there. The beetle benefits because the mites are stripping the carcass of what could be competitors for the carrion on which the beetle grubs live.

 

Beetle I.D provided by Guy A. Hanley at BugGuide, with some help from Anderson, R.S. & Peck, S.,1985, The carrion beetles of Canada and Alaska: Coleoptera: Silphidae and Agyrtidae, Insects and Arachnids of Canada Handbook Series, 13, 121 (pdf) Page 94 Figs. 37, 38. showed the base of elytra of Nicrophorus species (dorsal view) N. hybridus and N. investigator, which would otherwise be difficult to distinguish from each other.

For more on burying beetles visit:

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Posted in Alberta, Anatomy, Blog Link, Canada, Coleoptera, Entomology, invertebrates, macro, Phoresy, Silphidae, White Studio | Also tagged , , , , , , , , , 3 Comments