. Bulletin of the Department of Agriculture. Agriculture. 8 BULLETIN 431, U. S. DEPARTMENT OF AClRICI^LTURE. APPEARANCE OF A HEALTHY LARVA AT THE AGK AT WHKH IT DIES OF SACBROOD. The symptoms wliicli differentiate sacbrood from the other brood diseases are to be found primarily in the post-mortem appearances of the larva* dead of the disease. As an aid in interpreting the description of these appearances a description of the healthy larvae is first made. Larvre' that die of sacbrood do so almost invariably after capping and at some time during the four days just preceding the change in fo
. Bulletin of the Department of Agriculture. Agriculture. 8 BULLETIN 431, U. S. DEPARTMENT OF AClRICI^LTURE. APPEARANCE OF A HEALTHY LARVA AT THE AGK AT WHKH IT DIES OF SACBROOD. The symptoms wliicli differentiate sacbrood from the other brood diseases are to be found primarily in the post-mortem appearances of the larva* dead of the disease. As an aid in interpreting the description of these appearances a description of the healthy larvae is first made. Larvre' that die of sacbrood do so almost invariably after capping and at some time during the four days just preceding the change in form of the maturing bee to that of a true pupa. During the first two days of this prepupal period the larva moves about more or less in the cell and spins a cocoon. It is then com- paratively quiet for about two days, lying on its dorsal side and ex-. FiG. 4.—Lateral view of healthy worker larva showmg the normal position within the cell. For conven- ience of description the length is divided into thirds—anterior third (AT), middle third (MT) and posterior tliird (PT). Enlarged about 8 diameters. (Original.) tended lengthwise in the cell. At the close of this two-da}'" period of rest, as a result of the metamorphosis going on, the larva changes very rapidly to a true pupa, assuming the outward form of an adult bee. Although many larvae die of sacbrood durmg the first two days cr active period, of the 4-day prepupal period, by far the greater number of deaths occur during the last two days, the period of rest. A healtliy larva at this resting period of its development is chosen, therefore, for description. As dead worker larvae are the ones usually encountered in sacbrood and the ones almost invariably chosen in discussing the symptoms of the disease, the worker lai-va is here described. The normal larva hes extended in the cell (fig. 4) on its dorsal side, motionless, and with its head pointing toward the mouth of the cell. Its posterior or caudal end lies upon the bott
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