Microscopes and Magnifiers

Microscopes and magnifiers in beekeeping are used for two separate jobs: head-mounted magnifiers, magnifying glasses or magnifier lamps for seeing and correctly choosing a day-old larva during grafting; and stereo (dissecting) microscopes and light microscopes for examining colony health. A magnifier is a simple aid that improves acceptance and queen quality in grafting; a microscope reveals details invisible to the eye, such as nosema spores, tracheal mites and pollen. For definitive diagnosis and notifiable diseases, the laboratory is always essential.

Why is magnification needed in beekeeping?

Some beekeeping tasks are at or beyond the limit of the naked eye:

• Choosing larvae: The larva sought for grafting is freshly hatched, only slightly larger than a pinhead, and lies at the bottom of a comb cell.
• Examining diseases and pests: Nosema spores can only be seen under a light microscope, and the tracheal mite (Acarapis woodi) only by dissection under magnification.
• Examining pollen and honey: The shape of pollen grains shows which plant they come from; this examination is done with a microscope.
• Breeding work: Instrumental insemination of queens is carried out under a stereo microscope.

Which magnifiers are used for grafting?

Both hands are busy when grafting: one holds the grafting tool, the other the cell bar or the comb. That is why types that leave both hands free are preferred over a hand-held magnifier.

• Reading glasses and magnifying spectacles: The simplest solution for people with mild near-vision problems.
• Head-mounted magnifier: Magnifiers with interchangeable lenses worn on the head with a band or visor. Some have a small light. Low to medium magnification (a few times) is usually enough for grafting.
• Magnifier lamp: A lens on an arm with a ring of LEDs around it. It provides light and magnification together; suitable for an enclosed grafting room.
• Hand lens (loupe): Not practical for grafting, but it should be in the beekeeper's bag for examining a detail on a comb or a bee.

What to look for when choosing a magnifier

• Working distance: As magnification increases, the focusing distance between lens and comb gets shorter. There must be enough distance left to use the grafting tool comfortably; too much magnification makes the job harder.
• Field of view: At high magnification the field of view narrows, making it harder to move from cell to cell.
• Light: A magnifier reduces light; always use it with a strong, cool light.
• Comfort: A head-mounted magnifier should be light and not strain your head and neck during long sessions.

What is a stereo (dissecting) microscope used for?

A stereo microscope gives a three-dimensional image through two eyepieces, with relatively low magnification (usually tens of times) and a long working distance. The specimen can be worked on by hand or with instruments under the microscope.

• Tracheal mite examination: The bee's thorax is opened and the first pair of tracheae is examined.
• Identifying mites and pests: Useful for tasks such as distinguishing varroa from the smaller, more elongated Tropilaelaps mites, or recognising small hive beetle larvae.
• Morphology: Examining wing venation, hairs and body parts.
• Instrumental insemination: Instrumental insemination of queens is carried out with a special apparatus under a stereo microscope.

What is a light microscope used for?

A light (compound) microscope magnifies a thin preparation hundreds of times, lit from below. In beekeeping it is mainly used for two jobs:

• Nosema spores: The abdominal contents of bees are examined for Nosema spores. The spores are usually seen at about 400× magnification as bright, rice-grain-shaped bodies.
• Pollen analysis: The botanical source is determined from the shape of the pollen grains in a honey or pollen sample. This examination requires expertise; it is done in laboratories to determine the botanical origin of honey.

A simple microscope test for nosema

1. Take a sample: Collect about 30 bees from the hive entrance, preferably returning foragers. Young bees can give a misleading result.
2. Prepare: The bees' abdomens are crushed in a little water in a small container.
3. Make a slide: A drop is placed on a slide and covered with a cover slip.
4. Examine: Look for spores first at low magnification, then at about 400×.
5. Interpret: Seeing spores indicates infection; the density can be roughly assessed. The two nosema species cannot be reliably distinguished with a microscope; a laboratory is needed for a definitive diagnosis.

How are tracheal mites and varroa examined under magnification?

Tracheal mite

Tracheal mites cannot be seen with the naked eye. To examine for them, the bee's head and front legs are removed, the collar at the front of the thorax is lifted off to expose the first pair of tracheae, and they are viewed under a stereo microscope. Healthy tracheae are white and translucent; infested tracheae show brown-black patches and mites.

Varroa

Varroa destructor females are reddish brown, flattened crosswise and about 1.6 mm wide; they are visible to the naked eye. No microscope is needed for counting. A magnifier or stereo microscope is useful for seeing the mite's legs and developmental stages and for distinguishing it from the smaller, more elongated, fast-moving Tropilaelaps mite.

What does pollen look like under the microscope?

The pollen of each plant species has its own characteristic size, shape and surface pattern. Pollen is identified under the light microscope by looking at these features. Pollen analysis is used to determine which plants a honey comes from and to understand which sources bees are foraging on. Accurate identification requires a reference collection and experience.

What should you look for when choosing a microscope?

• Optical quality: Sharpness and contrast matter more than a high magnification figure.
• Illumination: Adjustable LED illumination does not heat up and lasts a long time.
• Robustness and portability: A light, sturdy body for use in the apiary; a fixed, vibration-free stage for the laboratory.

Care and hygiene

• Lenses: Wipe only with lens tissue and a suitable cleaner; do not touch with fingers that have propolis or honey on them.
• Dust: Cover with a dust cover when not in use.
• Specimens: Bees, slides and containers used in disease examination are destroyed so that bees cannot reach them; nosema spores can spread to other colonies.
• Magnifiers: Keep the grafting magnifier and lamp clean, free of jelly and wax smears.

Common mistakes

• Too much magnification for grafting: The working distance becomes too short to use the tool.
• Using a magnifier without light: The image darkens and older larvae get chosen.
• Taking nosema samples from young bees: The infection appears lower than it is.
• Treating a microscope result as a definitive diagnosis: Suspected cases should be confirmed in a laboratory.