Keep that big green stinkbug at arm’s length

...with North Saskatchewan River background.

…with North Saskatchewan River background.

A quick macro photography tip: when your subject is slow and compliant, and when regulations and common sense allow you to pull a branch, side shoot or flower stem from a plant (in your garden, or with weeds…don’t try this with wildflowers in any protected area!), try holding the subject at arm’s length against a distant backdrop, then move it slowly closer to the lens to find focus–you’ll be surprised at the results you get. This true bug, (Chlorochroa sayi Stål, 1872) was found on blooming Dogbane, sharing the flowers with a large mite.

Posted in Alberta, Bugs, Canada, Edmonton, Hemiptera, Insect, macro, Pentatomidae, photography, Season, Summer, Technique Tagged , , , , , , |

Rooted in Nature

Rooted III: Perspectives on the Natural World is on this Sunday, July 19, 10 am – 4 pm. I’ll be there with other artists displaying our views of nature. Drop by for a chat if you can make it!

Posted in Alberta, Art, Bugs, Canada, Display, Inspiration, macro, photography, Season, Summer Tagged , |

Why an Iridescent Beetle?

Dogbane Beetle, Chrysochus auratus (Fabricius 1775) photographed in white box with reflected flash.

On first glance, the Dogbane Leaf Beetle is a stunning metallic blue-green, that clearly stands out on the light-green Dogbane leaves it feeds on. However, when you look closer, you can see the highlights of the elytra and the pronotum change in colour depending on the viewing angle and the angle of the light source. Shades of copper, orange, yellow, blue and even a shadowy black emerge as the beetle moves around a leaf. How does this iridescent colour shift happen?

(The beetle above was photographed with reflected electronic flash while climbing up the walls in a white box)

The best open-access paper I could find on beetle colour was Gold bugs and beyond: a review of iridescence and structural colour mechanisms in beetles (Coleoptera) by Seago, Ainsley E. et al. The paper reviews all the different iridescence mechanisms known in Coleoptera, from both the entomological and optical (i.e. physics) literature. (From now on, the location of information made within the paper will be shown parentheses.)

Before looking at the mechanism that applies to our little metallic friend, I should define exactly what ‘iridescence’ means. The paper’s definition of iridescence is based on that of Mason (1927): ‘iridescence has for its main characteristic a change in the hue of the object exhibiting it as the angle of vision is varied’ (1.1), which is close to my observations in the first paragraph. The paper provides three mechanisms that can cause iridescence–multilayer reflectors, three-dimensional photonic crystals and diffraction gratings. For the family Chrysomelidae, in which the Dogbane Leaf Beetle resides, the common colour mechanism is multilayer reflectors (2.3).

Blue sky Rainbow

How are multilayer reflectors developed? When a beetle grub undergoes metamorphosis in the pupal stage, the epidermis secretes parallel layers of chitin to form the exoskeleton. These layers may be of different thicknesses and can be separated by other material so once they harden they refract light differently.

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(Visible light spectrum image from Wikipedia)

As I understand it, the optical properties of thick layers allow long wavelengths, like orange or red, to pass through while thinner layers pass shorter wavelengths such as blue. When we vary our viewing angle or if the angle of the light source changes, we are lengthening and shortening the wavelengths of light in different areas. The refracted light can merge (e.g. green + yellow = orange) and change the colours that are reflected back. (2.1) (See fig 2 online to for the different types of multilayer reflectors.)

Dogbane Leaf Beetle, Chrysochus auratus (Fabricius 1775)

Not obviously cryptic… Dogbane Leaf Beetle on Dogbane.

So why have these bright eye-catching iridescent metallic colours anyway? What evolutionary function does this have? Considering their iridescence is primarily green, the most obvious answer is crypsis, the ability to remain unobserved. However to my eye, the beetle is highly visible even in green leafy surroundings, but that may not the case for potential predators. The fact that these beetles are often seen brazenly exposed on leaf surfaces, sometimes even when mating (see previous post) shows that there may be an aposematic (warning) element to their coloring. Their food plants are Milkweed and Dogbane, both of which have sap containing toxic cardenolides. Dogbane beetles can sequester (store) cardenolides and are known to release them from pronotal and elytral glands, and this may discourage some predators and parasites.

 

References

Dobler, S., D. Daloze, J. Pasteels. 1998. Sequestration of plant compounds in a leaf beetle’s defensive secretion: cardenolides in Chrysochus. Chemoecology, 8: 111-118.

Mason C.W. Structural colors in insects, 3. S. Phys. Chem.1927;31:1856–1872. doi:10.1021/j150282a008 [Ref list]

Seago, A. E., Brady, P., Vigneron, J.-P., & Schultz, T. D. (2009). Gold bugs and beyond: a review of iridescence and structural colour mechanisms in beetles (Coleoptera). Journal of the Royal Society Interface, 6(Suppl 2), S165–S184. doi:10.1098/rsif.2008.0354.focus

Animal Diversity Web — Chrysochus auratus

 

Posted in Alberta, Bugs, Canada, Chrysomelidae, Coleoptera, Edmonton, Insect, macro, photography, Season, Summer Tagged , , , , , , |

Birch Leaf Miner

As a lapsed horticulturist, I am well aware of the leaf miners and the damage they can do to trees. I see the symptoms of them often on my nature wanderings or when working in the garden: patches of leaf that are discoloured, sometimes with tunnels visible, created by little larval miners excavating between the leaf surfaces. These larvae are usually either from moths, flies or–on birch leaves–by sawflies. Damage to the leaves can be extensive at times, and reoccurring attacks can weaken the tree and cause branch dieback and eventually death.

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Leaf miner damage on Paper Birch leaf.

We have three Paper Birch (Betula papyrifera) in our garden in Edmonton, and while prowling through the front garden for photo op’s I came across some birch leaves that showed the typical damage of a leafminer, visible at eye level on the lowest branches of the tree. I decided to photograph the leaf, mostly with the thought that I would be able to share the images on a new garden blog that I have been planning. Because I could see that there was something under the papery damaged area (above) and because I had been playing with backlit leaves recently, I decided to try the technique on this birch leafminer damage. I simply pressed the leaf directly against the flash lens and adjusted the flash power settings manually until I had the right exposure.

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Leaf miner damage photographed with backlighting. The dark spots accumulating on the right is frass (poop) while the single larva is on the left. Note the pattern on the larva.

I was somewhat surprised to see some detail in the larva, including some prominent dark marks on the segments behind the head. I emailed the images to Greg Pohl at the Northern Forestry Centre, who was able to identify it as the larva of Fenusella nana (Klug), the Early Birch Leaf Edgeminer, as determined from the key found in the paper Current status of invasive alien birch-leafmining sawflies (Hymenoptera: Tenthredinidae) in Canada, with keys to species by Digweed, S. C., et al (2009).

Searching online, I found Creative Commons images of the larva:

Desktop

Fenusella nana. Left: ventral view of the thoracic segments. Centre: full dorsal view. Right: full ventral view. CC 2007 W.N. Ellis, Zoölogisch Museum Amsterdam

I could not find a CC image for the adult, but there are a variety of photos at BugGuide that give a good idea of its appearance and the damage it causes.

There are five species of leaf mining sawfly (not a true fly but a Hymenopteran related to wasps, bees and ants) that effect birch trees across Canada, and all are alien invaders. In Canada, two species (F. pumila and P.thomsoni)  have been successfully controlled with releases of parasitoids, however, F. nana has yet to have that pleasure.

The life cycles of birch leafminer sawflies are all similar. F. nana adults are active mid-May to June, when the females use their saw-like ovipositors to lay up to three eggs at the leaf edge. The larva hatch and go through five or six instars between the surfaces of the leaf, overwintering in the last instar to pupate in spring.

References

Digweed, S. C., MacQuarrie, C. J. K., Langor, D. W., Williams, D. J. M., Spence, J. R., Nystrom, K. L., and Morneau, L. (2009). Current status of invasive alien birch-leafmining sawflies (Hymenoptera: Tenthredinidae) in Canada, with keys to species. Canadian Entomologist, 141(3), 201-235. DOI: 10.4039/n09-003.

Langor, D.W.; Digweed, S.C.; McQueen, R.L.; Spence, J.R.Where have all the birch leafminers gone? Forest Insect and Disease Notes, August 1996, A-033

Canadian Forst Service Publications on Birch Leafminer.

City of Edmonton  Insect Identification & Advice: Birch Leafminer.

 

 

 

Posted in Alberta, Bugs, Canada, Edmonton, Equipment, Flash, garden, Hymenoptera, Insect, macro, Parasitoid, Season, Spring, Summer, Technique, Tenthredinidae Tagged |

Intermediate Macro Photography Workshop

Coming this Saturday, July 4, 2015 @ 9:00 am – 4:00 pm at the Ellis Bird Farm, the first Intermediate Macro Photography Workshop!

This day-long workshop is aimed at photographers who have previously taken the Introduction to Macro Photography course or for those familiar with their cameras, manual exposure and who have some experience using flash with macro.

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Posted in Alberta, Camera, Canada, Education, Equipment, Flash, Insect, Inspiration, macro, photography, Season, Summer, Technique, White Studio, Workshop Tagged , , , |

Dogbane Leaf Beetle

Dogbane Beetle, Chrysochus auratus (Fabricius 1775)

Dogbane Beetle, Chrysochus auratus (Fabricius 1775)

This has got to be one of the shiniest leaf beetles in Canada and I was glad to come across them this hot summers’ day when I was feeling down and dispirited. As their name suggests, these beetles feed on Dogbane (Apocynum sp.), a plant known for its poisonous milky sap. The beetles are able to sequester the poisons from the host plants and are then able to use them as defence against predators by secreting them from pronotal and elytral glands.¹

 

Just spending 25 minutes with these metallic marvels brought me round to my usual benevolent self, ready to face the trials and tribulations of  life once more.  :)

Photographed 27 June 2015, in the North Saskatchewan River valley, Edmonton.

¹Dobler, S., D. Daloze, J. Pasteels. 1998. Sequestration of plant compounds in a leaf beetle’s defensive secretion: cardenolides in Chrysochus. Chemoecology, 8: 111-118.

Posted in Alberta, Canada, Chrysomelidae, Coleoptera, Edmonton, in copula, Insect, macro, Mating, photography, Season, Summer Tagged , , |