Seasonal snapshots of nature in close-up

This month's issue completes our first year of Walks

This month, we look at just one subject, a bee, to illustrate that a single insect can provide a wealth of study on both the macroscopic and microscopic scale.

In addition, to complete a full year of Walks, we look at ways of photographing nature for the 'Web'. Why not capture nature in close-up in your part of the world and submit a few favourite images to us. We would be delighted to compile a selection of these international snapshots for the Micscape magazine!

Next month, Maurice Smith will continue the walks, while the author will be starting a new challenge. A series on the world in close-up around the home .... looking at all those items we take for granted around the home and office but which can be fascinating in close-up.

Please read the important notes on collecting.

At this time of year you can often find insect casualties during a walk. I found the bumblebee above on my back doorstep, which prompted me to use it as the basis for this month's issue. If you find one of the larger insects dead such as a bee, why not have a really good look at it under a 10x lens or a stereo microscope. The larger ones are easy to 'dissect' to inspect the legs, head, body and hairs etc more closely.

If you have either a 35mm camera or camcorder with a 'macro' facility you could compile a short snapshot or video sequence of the insect's structure as a class project if you are a student.

Bumblebees are a relatively large and hairy social bee belonging to the genus Bombus. Different species can usually be distinguished by the patterning and colours of their body hairs, I think the one shown is Bombus lucorum a common UK species. Unlike the familiar honeybee (Apis melliferae) which forms permanent colonies, the bumblebee forms annual colonies. Only the mated queens usually survive the winter to start new colonies in the spring, often at the base of tall grass or in old mouse holes.

The bee has two pairs of wings and one pair (of the fore and hind wings) is shown on the left. Bees are part of the immense order of insects called Hymenoptera which also includes ants and wasps amongst others. In this order the wings are joined by a row of minute hooks on the leading edge of the hind wing. Note that the wing venation is quite simple and produces a network of large and often square 'cells' which is typical of this order. If you compare the venation with a dragonfly for example, the latter have much more complex venation and smaller 'cells'. Insect wings have many fascinating features and are worth examining under the compound microscope to study the hair structure, venation and the hooks mentioned above. The image right shows a closer view of the wing.

Insect heads are particularly fascinating to study in close-up because the the eyes, antennae and mouthparts can be examined. Under a stereo microscope you may need to use a good strong external light source and to vary the lighting angle to see the details on the dark head. The image right shows the bumblebee's compound and simple eyes. The simple eyes or ocelli are the three black beads in a row at the top of the head. The ocelli are simple structures and can only detect light, darkness and movement. The compound eye is made up of a number of hexagonal facets which resembles a honeycomb. The number of facets effects the visual acuity and varies amongst different insect species, the housefly for example has 4000 facets whereas the dragonfly has up to 28000. The honeybee's eye is estimated to have one per cent of the visual acuity of a human eye.

Body hairs
Bumblebees are hairier than the honeybee and possess dense bands of coloured hairs (see image left). The hairs are long enough to easily snip off with a small pair of scissors, and they can be mounted dry under a coverslip on a microscope slide to examine at higher magnification using a compound microscope. A selection of hairs are shown right using dark-ground illumination and a 9x objective (screen magnification 120X) which highlights the structure of the semi-transparent hairs (diameter 15-25 microns) quite clearly. The author, who had never examined these hairs before, was intrigued to find that each hair had an intricate structure.

Examining the three pairs of legs will reveal the detail of the claws, hairs, spines and structure of the jointed limbs. The legs play an important role in bees during pollen collection.

Four main regions can usually be distinguished in an insect leg. The coxa is the basal segment which joins the leg to the thorax. Then comes the femur which is usually the longest segment, followed by the tibia which can be longer but is usually more slender than the femur. Finally the tarsus or foot which has 1-5 segments and bears one or two claws at the tip.

The image left of the bumblebee's hind leg shows the base of the femur (note the long spine), the tibia, segmented tarsus and two claws.

The bees, particularly the honeybee, are probably one of the most well-studied insects by microscopists because of the bee's economic importance. Many beekeepers are expert microscopists because bees are susceptible to parasites and infections. Beekeepers can deduce a great deal of the well-being of the bee and beehive colony by examining the bee both externally and internally. (See link to an article on Varroa, a bee parasite below.)

If you are interested in carrying out a proper dissection of a bee (or other insect) particularly with a view to preparing a set of insect parts as permanent microscope slides, an excellent series of booklets are published by Northern Biological Supplies (UK) (follow Shop links). These are available as separate booklets (eg on bee, insect, or arthropod dissection) or as a bound set of booklets sold as 'Practical Microscopy'. All the materials and equipment required to prepare permanent slides are discussed.

Final thoughts:
So that's it folks, after a year of these Nature Walks I hope I've managed to pass on some of my enthusiasm for the wonderful close-up world of nature around us. Even if you never buy a microscope, do treat yourself to a 10X hand-lens and carry it when you're on a country walk or just wandering around the garden. There's so much of interest to see at any time of the year both on the macro- and microscopic scale.

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Suggested reading
Capturing nature in close-up for the Web - a special supplementary article showing the ways you can capture images, and shows how the author produces this Walk series.

Read an article 8X More, on choosing and using a hand lens, and even find out how you can take video pictures through it.

Northern Biological Supplies (UK), produce excellent booklets on insect disection and preparing permanent mounts on microscope slides.

Most libraries will have books on Invertebrate Zoology which cover insect structure in detail.

Image details
Camera images were transferred to the PC using a Creative Video Spigot capture card.
Image manipulation using Photostyler v2.0 software.

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The author Dave Walker is a UK based amateur naturalist keen to encourage people to explore nature in close-up.

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