. Diseases of bees. Bees. 16 BULLETIN 810, U. S. DEPAETMENT OF AGEICTJLTUKE. the food of the larvae by means of a capillary pipette made from glass tubing of small bore. Care must be exercised in thus feeding the larvae. Too much of the suspension will often float the larva. There is danger also that it will be changed in position mechanically by means of the feeding pipette. In either event the chances are that such lars'ae will be removed subsequently by the bees. Consider- able larval food already in the cell is advantageous. This method has proved to be especially useful in much of the exp
. Diseases of bees. Bees. 16 BULLETIN 810, U. S. DEPAETMENT OF AGEICTJLTUKE. the food of the larvae by means of a capillary pipette made from glass tubing of small bore. Care must be exercised in thus feeding the larvae. Too much of the suspension will often float the larva. There is danger also that it will be changed in position mechanically by means of the feeding pipette. In either event the chances are that such lars'ae will be removed subsequently by the bees. Consider- able larval food already in the cell is advantageous. This method has proved to be especially useful in much of the experimental work recorded in the present paper. It has the advantage of being both economical as to the number of colonies needed, and definite. Dur- ing the third day following the hour of inoculation symptoms of European f oulbrood will be observed if infection is pro- duced. By the fourth day fre- quently all of the infected lar- vae will have been removed by the bees. Symptoms of Euro- pean foulbrood infection mani- fested by larvae sick rather than dead have proved to be espe- cially useful for experimental purposes in these studies. During most of the time that experimental studies are being made it is necessary to have fresh diseased material at hand. A supply can be main- tained by using one or more colonies for this purpose. Re- peated inoculations of the col- ony usually must be made at intervals of a few days or after longer periods, depending on its condition and the need for the virus. The indirect method is especially indicated in inoculating these colonies. Frequently colonies which have been employed in European foul- brood experiments can be used again for further experiments on the disease. This must be done with some care, however. The condition of the brood always should be noted before an inoculation is made. European foulbrood colonies serve very well the purpose of experi- mental colonies for the other brood diseases and for Nosema-disease. In fact, not inf
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