HUMBLE BEES.

Otago Witness, Issue 2010, 1 September 1892, Page 24

HUMBLE BEES.

TO THE EDITOR Sin,— ln an article which appeared in the New Zealand Journal of Science of January 1891 (p. 16), I made the following statement as to the introduction of humble bees into the colony :— "At the very outset a mistake seems to have been made which shows how much in the dark many of those are who guide the community in acclimatisation matters, and how largely chance often bulks in the final results of such experiments. Red clover (Trifolium pratense) differs from white clover (T. repeps) and many other papilionaceous flowers in having its nectar secreted at the base of a tube 9 to 10 mm. Cabout two-fifths of an inch) long, formed by the cohesion of the nine inferior stamens with each other and with the claws of the petals. Instead, therefore, of an insect being able to thrust its trunk down to the nectary by the two small openings which lie one on each side of the superior stamens, as in white clover, it must insert it directly down the staminal tube. Only 111 this way can the insect receive a dusting of pollen, and so ensure cross fertilisation of the flowers, without which this species is practically sterile, In order to roach the honey in

this way, an insect must possess ft proboscis at least 9 to 10 mm. long. This fact was probably not known to anyone In New Zealand when the importation of humble bees was decided upon. Only the fact was known that humble bees were the principal agents in fertilising red clover, and In sending for these insects the species which is probably the most abundant in England— vifc, Bombus terrestris— was selected. According to Hermann Mifller, who is the best authority on the subject, B. terrestris docs not enter tne flowers of red clover in a legitimate way and so brings about cross fertilisation, but always^makes a hole near the base of the flower and sucks the nectar through this. Its trunk is not than from 7 to 9 mm. long, so only the largest females could reach tfie base. of^the flower. On the other hand, it is the case in Germany at least that no less than 12 other species of Bombus or humble bees having trunks varying from 10 to 15 S in leffch, legitimately visit and fertilise the re in Cl thfsame article I mention the occurrence, as recorded by Professor Hutton, of .black humble bees in Christchurch, and this variety has since spread widely over this island. I haye never been able to explain the fertilisation of the red clover in New Zealand since the humble bees were iatroduced. Either the flowers here were producing shorter tubes> or the bees were producing longer trunks, both suppositions being equally unlikely to occur so suddenly. . # Exactly the same difficulty met me in seeking to explain the fact that the various species and hybrids of Primula growing in our gardens were producing seed vessels naturally since the advent of the humble bees. Bombus terrestris cannot reach the nectar, which lies at the bottom of a tube at least 12 mm. long, and always bites a hole in the side of the tube. These facts led to doubts as to whether we had not more than one species of Bombus in the colony, and Mr W. W. bmitn, of Ashburton, who has perhaps devoted more attention to tne subject than anyone else, sent Home at the end of last summer a large series of bees to'Mr Saunders, editor of the Entomologist, end asked that gentleman to clear tip the difficulty. Mr Smith has kindly forwarded to me Mr Saunders' letter, from which I gather the following :— Tlie series sent included one male and one female of Bombus terrestris, all the rest were varieties of Bombus hortorum. The latter can be distinguished from the former by the much treater length of face, as well as by the sharper efinition of the yellow or orange band on the abdomen. (He does not specify to which form our black variety belongs.) The most distinctive character by which the different species of Bombus may be recognised is, however, the structure of the genital armature, a feature which can only be satisfactorily compared with the aid of diagrams. This identification of the matter clears up the difficulty at once, for B, hortorum is a bee having a trunk from 18 to 21 mm. long, so that we are now spared the necessity of trying to explain how our bees came to have such long trunks, a fact which has somewhat puzzled me for some time. In conclusion, it is worthy of remark that B. hortorum was never observed by Muller to visit; red clover in Germany, and his observations extended over a long series of years. —I am, &., George M. Thomson. Dunedin, August 23. . P.S— The perfectly or imperfectly brown banded varieties of humble bees are Bombus horlorum, var. suhterraneus, while the blacK varieties without bands are var. Harnsellus.