B I O M E T R Y
Text and illustrations - extracts from the CDROM
"The Honeybee and Man"
(with kind permission of the author : Bernard Leclercq)
|Both Entomologists and beekeepers were quick to observe differences between
honey bee populations from various parts of the world and even from region to region.
The first morphological observation was bee colour, as it was the most visible attribute.
Advances in scientific knowledge, gave birth to biometry, the science of measuring morphological characteristics, and opened the door to a new accurate method of classifying different races of bees.
Biometry occupies an important place in most breeding programs and in the conservation of any determined race.
Information about a race, such as its purity or hybridisation can be obtained by measuring certain characteristics.
To measure the length of the tongue, the head is cut off and pinned (needlework pin) to a soft surface (cork). The tongue is carefully pulled straight with a pair of fine tweezers. If there is too much traction, the tongue might stretch and falsify the measurement or it might even tear out: there should be just enough pressure to keep it straight but not enough to see the root of the tongue.
If the sample bee is not fresh, it is advisable to moisten the tongue with a small brush to dissolve any crystallised sugars that could make the tongue brittle.
Measurements are taken under a dissecting microscope with a magnification of 10x to 20x.
The dimension required when measuring the tormentum is the width of the hairy part in the centre of the 5th dorsal abdominal segment. Measurements are taken under a microscope with a graduated lens.
To facilitate the procedure and make sure that the whole width of the tormentum can be seen, stretch the body of the bee with a small pair of pincers or tweezers. This will reveal the part of the tergite hidden under the 4th abdominal segment.
The cubital index of the forewing is the most reliable characteristic for distinguishing between similar populations of honey bees and to determine their degree of hybridisation.
The other measurements ( pilosity, length of tongue, width of tomentum, etc.) can only confirm the results obtained by a detailed analysis of graphs of the cubital index. This index is the ratio between the length of two segments ( A and B ) of the third cubital cell of the forewing.
To ensure reliable results and produce graphs showing the distribution of the measurements taken, at least 100 bee wings have to be analysed before obtaining an average.
This can vary greatly in different countries and regions. For example, the strain of Apis mellifera mellifera found in the South of France has a higher cubital index than the same species near the Siberian border.
Therefore, due to geographical and climatic conditions, even within the same species there are numerous ecotypes of Apis mellifera mellifera (see races).
The method for measuring pilosity consists of measuring the longest hairs in the centre of the 6th tergite using a magnification of approximately 30x or 40x. To do this the microscope needs to be fitted with a micrometric lens.
Text and photographs by Bernard Leclercq