1258 A TEXTBOOK OF THEORETICAL BOTANY 



90 flowers in one journey and a colony working a field of Buckwheat would 

 visit about 50 million flowers for every pound of honey collected. This 

 gives some idea of their value as pollinators. 



There are relatively vast difl'erences between the amounts of nectar 

 secreted by different flowers. Fagopyrum only secretes an average quantity 

 of 0-3 mg. per flower. At the other extreme is Liriodendron, which secretes 

 nectar only on the first day of opening and on the following morning. 

 Its average production is 1-64 gms., varying between 3-16 gms. and 



0-47 gm. 



Nectar flow is frequently intermittent and the factors which control it 

 are not fully known. Some species may only produce a copious flow every 

 few years. Both amount and concentration may vary independently. In 

 Antirrhimim it has been observed that a dry or badly aerated soil reduced the 

 yield but increased the concentration of the nectar, while cold reduced the 

 yield but did not affect the concentration. In qualitative terms, temperature, 

 relative humidity, soil moisture, soil type, day length and possibly altitude, 

 all play a part in determining the amount of the nectar flow. 



Differences in quantity are, however, of less importance than differences 

 in the concentrations of sugars, to which bees are remarkably sensitive, 

 ignoring copious but dilute secretions in favour of richer yields. Thus Pear 

 blossom seems to offer no attraction to bees except in the morning. As the 

 day goes on, the Apple and the Plum offer better fare as the concentration 

 of their nectar increases. Blow-flies on the other hand always find the Pear 

 attractive. There is thus a good deal of " competitive bidding " between 

 species for insect visitors. 



When one considers that the average water content of ripened honey is 

 about 10 per cent., while that of the fresh nectar may be 75 per cent., so that 

 the weight of nectar collected is about four times that of the honey produced, 

 the need of economy of labour by the bees is evident. 



In a fully grown colony of 50,000 bees there may be 30,000 field workers. 

 If each of these makes ten journeys per day this means 300,000 loads of 

 nectar. An average bee-load of nectar is about 025 mg. and about 

 70,000 loads of nectar go to make one pound of honey, so that a full colony 

 may win about four pounds of honey each good day. The more concentrated 

 the nectar collected the greater will be the return in honey for a given 

 number of journeys. Average concentrations, under a variety of conditions, 

 for the principal fruit blossoms are given below: 



Apple 35-55% P^"™ 10-40% 



Cherry 20-50% Pear 2-17% 



Peach 20-25% 



Nectars with less than 5 per cent, of sugars have little or no attraction 

 for hive bees. The table below, taken from Vansell, gives some average 

 figures for the concentrations in a number of common plants and illustrates 

 the wide variation which exists. 



