1. The blood of the larval honey bee at different stages of development has been subjected to the chemical analyses customary for routine examination of human blood. Certain of both the organic and inorganic constituents vary widely from the mammalian values.
2. Of the organic constituents, sugars are above normal for the mammal during the feeding period, but during pupation reach a level comparable to the mammalian level. Amino acids are 50 times higher, proteins slightly lower, fats higher than in the mammal.
3. Of the inorganics, the sodium and chlorine are very low, potassium, phosphorus, calcium, and magnesium high, and total salt content much lower than in mammalian plasma.
4. Osmotically the amino acids are the most effective fraction, having almost twice the value of the inorganic salts. Changes in sugar content with changed activity account for a large part of the lowering of the osmotic pressure during pupation. Roughly
90 per cent of the osmotic pressure can be accounted for by the constituents detected by analysis.
5. Combination of calcium with amino acids to unionized compounds probably holds part of the calcium in solution, since a prepared salt solution with the analyzed salt concentrations precipitates at the pH of the blood.
6. A solution of amino acids separated from a casein tryptic digest has an osmotic preasure considerably higher than can be accounted for by the known constituents. It is possible that similar metabolites may be present in blood to account for the unexplained fraction of its osmotic pressure.
A hypothesis is presented to explain the developments of epizootics of nosema disease of the honey bee, Apis mellifera Linnaeus. It is assumed that most hives contain some lightly infected carrier bees in which the numbers of the parasite increase very slowly. But under the influence of certain conditions the parasites within these bees increase in numbers very quickly, and, if other conditions are favorable, an epizootic of the disease will develop. A hypothetical course of development of an epizootic is described. It is suggested that the numbers of the parasite increase when the metabolism of infected bees is changed so as to change the environment of the intracellular parasites. Changes in the metabolism of infected bees are considered to be stress reactions in the bees as a result of disruption of their behavior patterns when the hive is disturbed. Disturbances to the hive are considered to be due to management, weather, and other external factors.
A 2-year survey of the incidence cf nosema disease of the honey bee in South Australia bas shown that a spring peak of infection may be expected each year. The level of infection is at a minimum in midsummer and winter but a rise may occur in the autumn. It was considered that the disease, either in the form of a few infected bees or of spores on the combs, was present in all hives throughout the survey. Significant differences in the level of infection between hives in the same apiary suggested that there may be factors, varying in some way from hive to hive, which determine the level of infection within each hive. In view of the appreciable variation between hives it is evident that the incidence of the disease in individual hives was estimated with unnecessarily high precision with samples of 100 bees, and that in future surveys samples of 20 to 25 bees would be adequate in most circumstances.
In an earlier paper we reported the identification of geraniol as a predominant component of the scent which is produced by the Nassanoff organ of the honey bee. Field tests by Free and unpublished observations of our own, however, showed that geraniol was much less attractive to bees than was the complete scent. Therefore, an attempt was made to detect and identify other fractions of this scent and test these on bees.
The worker ovaries of 16 species of stingless bees and two subspecies of European honeybee were studied under the queenright condition. In contrast to the honeybee, which showed, as already well known, no trace of ovary-development, the ovary-developed workers were observed in the nurse bee stage of ail stingless bee species, in a very high frequency, except for Trigona freiremaiai (Moure), T. (Meliponula) bocandei (Spinola) and T. (Partamona) cupira Smith. In the observation in T. (Scaptotrigona) postica Latreille, the ovaries were still rudimentary at emergence, developed at the stage of nurse bee in parallel to the pollen intake, then degenerated in the subsequent stages. Histologically, the ovary development follows the manner seen in other polytropic type ovaries, though considerably modified. In all species examined, however, the synchronous occurrence of more than one mature oocyte in each ovary was never observed. Further, some considerations were given concerning the development of worker ovaries from the comparative and evolutional standpoints.
Norms were established for respiration, growth, and tissue composition of 0- to 72-hour-old female honeybee larvae reared in the laboratory on natural royal jelly and worker jelly diets. The worker jelly diet was then altered experimentally in the direction of royal jelly through additions of sugar and certain water-soluble acids of unknown structure extracted from royal jelly, but present in the natural diets of larvae of both female castes. In general, developmental norms were shifted in the direction of the norms of larvae fed royal jelly, but the changes were not fully co-ordinated. The added acids were strongly growth inhibitory. A high inverse association between the total water-soluble acid content of the diet and larval weight suggested that the acids may represent a nutritional growth-regulating mechanism. The evidence indicates that nutrient balance is significant in the early development of the dichotomy between female castes, and that no single constituent determines the ultimate development of either caste.
Histological evidence is presented for a caste difference in endocrine activity during the critical period of determination in the larval honeybee. Until the Last larval instar, neurosecretory cells in the brain of the honeybee larva remain undifferentiated. During this undifferentiated period there is a quantitative difference in apparent activity, as evidenced by the frequency of occurrence of cytoplasmic particles in certain large neuroblasts. Whereas the histological criteria for neurosecretory cells cannot be fulfilled, the brain is presumably exercising a regulatory role in growth and development. These large neuroblasts with phloxinophil inclusions are the likely candidate cells. Between the ages of 40 and 80 hours there is considerably more activity in the queen larva than in the worker. At this time the corpora cardiaca are non-existent as discrete organs.
Changes in size and histological appearance of the corpora allata indicate a progressive increase in activity during the first 3 days. In the queen, nuclear degeneration with an apparent cessation of activity occurs in the third and fourth instars. In the late larval and propupal stages a reorganization occurs. This reorganization is characterized by the reappearance of a discrete nuclear membrane and well-defined nuclei. The presence of intercellular spaces...
1. The respiration rates of individual adult worker bees confined in small gauze cages were determined over a range of temperatures between 7 and 46° C. The respiration rates usually remained constant over a period of 1 hr., although at 7, 12° C., and possibly at 17° C. there were indications of a decrease with time, and at 42 and 46° C. indications of an increase with time. Fluctuations which would have reflected variable activity during any of the experiments were rare.
2. At each temperature studied the respiration rates increased progressively from the youngest adults (newly emerged) to the oldest measured (24-33 days). The increase was particularly marked during the first few days of adult life.
3. The respiration rates of newly emerged and 18 hr. old adults increased progressively between 7 and 46° C., but 4-33-day-old bees showed two peaks (at 17 and 46° C.) with a depression having a minimum value at 32° C. lying between. 2-day-old bees had similar peaks at 22 and 46° C.
4. It is suggested that the first peak in the respiration rate of the older bees occurred at the lowest temperature at which free movements were possible, and that it indicated an increased body temperature maintained by the bees to combat the effects of the low environmental temperature. The lack of this first peak in the case of the youngest bees is thought to mean that they were unable to raise their temperature above that of the environment. The information obtainable from the literature supported these conclusions; their implications in relation to the regulation of temperature within the colony are discussed.
5. Numerical values for the oxygen consumptions of adult bees are discussed in relation to those found by other workers.
The oxygen consumptions of drone and worker honey bee larvae were determined at 32. over the period between hatching 1Ind the sealing of the cells prior to pupation. A decrease in respiration rates with increasing age was found in both drone and worker larvae when the rates were calculated 011 a unit weight basis, but in both castes the oxygen consumption per larva rose rapidly in the period following hatching, subsequently increasing less rapidly. Drone larvae consumed greater amounts of oxygen than worker larvae of the same weight, and this was apparently linked with their more rapid increase in weight.
Four hundred and thirty records of the numbers of bees in honeybee colonies and of the amounts of brood and pollen present have been kept during various months of the years 1945-53, and the data have been used to calculate total and partial regression coefficients showing the influence of stored pollen and of colony size on brood rearing throughout the year.
It was found that pollen storage and colony size were correlated but that, even allowing for this, colony size and pollen both independently influenced brood rearing.
The annual distribution of the total regression coefficients of brood on pollen was somewhat similar to the brood curve itself, rising from a minimum in October and November to a maximum in midsummer, while the partial regression coefficients showed less clearly marked but similar features.
Both total and partial regression coefficients showing the influence of colony size on the amount of brood reared were also at a minimum in October and November, but reached their peaks in May.
The quantities of brood present in these colonies at Aberdeen, Scotland, followed a pattern similar to that given by Nolan for colonies near Washington, D.C.
Honey bees, artificially infected with Nosema apis Zander and introduced into an enzootically infected colony in summer when infection was naturally diminishing, were all infected and developed similar numbers of spores to those in naturally infected bees in spring when infection was high. This, and other evidence, suggests infection is not naturally suppressed by increased environmental temperature, but by reduction of infective fecal matter of the bees, which do not transmit infection to young individuals in summer.
Larvae, artificially infected when 0 to 1 day old with Streptococcus pluton (White) and placed in colonies, were usually ejected by adult bees. Ejection was delayed from colonies deprived either of unsealed brood or their queen, or which were reinforced with adult bees. The feces of surviving larvae whose weight was subnormal, contained many viable cells of S. pluton. Colonies reinforced with unsealed brood removed more infected larvae than usual. It is concluded that infected larvae are ejected when larval food is merely adequate, as it may be when a colony is growing rapidly ; and they are kept when larval food is more abundant, as it may be when brood rearing is retarded.
Natural outbreaks of disease occurred when brood-rearing, in colonies heavily infected with S. pluton, was increasing during nectar flows, which was also when secondary infection with Bacterium eurydice White increased. At such times, larvae heavily infected with both organisms may die quicker than they are being removed. At the same time infection of new larvae with S. pluton seemed to decrease: transmission of S. pluton was presumably checked by the death and ejection of unsealed larvae. Thus outbreaks usually seemed to be self-limiting.
Colonies eject introduced larvae even more readily after the main nectar flows which may account for the difficulty in causing disease artificially at this time.
Result of preliminary experiments have shown that European foul brood disease of the larval honeybee can be caused in bee colonies by spraying their brood with suspensions of Streptococcus pluton (Bacillus pluton White) and Bacterium eurydice White if the two organisms are grown together in mixed anaerobic culture ; fifth subcultures of a mixed culture were usually virulent, although virulence diminished rapidly after further sub-cultivation. It was not possible to cause the disease by simultaneous inoculation with separate cultures of the two organisms. As there is a tendency for colonies of S. pluton and B. eurydice to grow within, or upon, each other on agar in anaerobic cultures, the separate cultures of each organism were subcultured five times to try to ensure the exclusion of the other. The results of these experiments showed that virulence was maintained by one or both organisms in mixed culture, but the possibility remained that only one of the organisms was pathogenic; its virulence may have been maintained by the growth of the other which may, in vivo, be a secondary invader of the diseased larva ...
THE cause of European foul brood was originally thought to be Bacillus alvei or a mixture of B. alvei and Streptococcus apis. The causative organism was later named and described by White as Bacillus pluton, a lanceolate Gram-positive bacterium. This organism is the first of several which have been found to appear in diseased larvæ. However, White and others failed to culture B. pluton in vitro and it was afterwards considered to be a dissociant form of Bacillus alvei, of Bacterium eurydice, or of both. Others have maintained that B. pluton is a separate organism. It has been pointed out that Streptococcus pluton would be a more suitable designation than Bacillus pluton both on morphological grounds and in the absence of evidence that it forms spores. For these reasons and those given below the organism will be referred to as Streptococcus pluton.
Results obtained during investigations on Nosema apis at Rothamsted indicated that transmission of the disease from diseased bees to healthy bees virtually ceases during the flying season, and that the primary means of transmission of the disease from year to year is comb which has been soiled by excreta during the winter.