2.1.5. Obtaining larvae for grafting
Grafting is easier if the larvae can be removed from dark combs (combs from which 8-10 worker generations have emerged). Before use, dark combs should be placed close (next) to brood combs so the bees will clean and polish the cells for egg laying.
If many larvae from a single queen are to be grafted on certain dates, it is very useful to confine the queen to single combs for 12 - 24 hours four days prior to grafting. After this time, the comb with eggs can be transferred to a queenless nurse colony or can be retained in the brood nest of the source colony. There are several commonly used methods of making queen-confining cages (Morse, 1979):
- A simple method is to use a push-in cage made with wire mesh (with 4 mm spaces) or queen excluder. Push-in cages are usually about 12-15 cm2. Worker bees move through the holes in mesh as easily as they do in queen excluders. Sometimes the workers bees will chew the comb around the edge of a push-in cage and may release the queen within two days.
- If a breeder colony is to be used for an extended
period, the use of 3-5 comb isolators, made from metal queen excluder, is recommended.
The isolators are placed in the centre of the hive. One of the combs should
have abundant pollen. The remaining space is filled with one empty comb, sealed
and emerging brood and one comb with unsealed honey. Each 24 hours, one comb with
eggs is removed and replaced by an empty one. After the four days, larvae on
the first comb will be ready for grafting. The system allows for continuous
grafting of large cell numbers every day.
One of the best and most convenient methods of obtaining larvae is to use a special full depth hive body insert (Laidlaw and Page, 1997). The breeding queen is confined to three small combs, each about half the size of standard combs, in a compartment with sides made of queen excluder that makes up half of the insert. Three additional half-combs occupy the other half of the insert, which has open sides (see photo in Laidlaw, 1979). A standard comb well filled with pollen is placed next to one side of the insert, such as to the left, and combs with sealed or emerging brood are put in the remaining spaces of the body. Each day a centre comb with eggs is moved from the queenright partition to the non-excluded half of the insert as described by Laidlaw (1979).