INSECTS SUCKING THE SAP OF TREES. 171
had their heads more or less deeply inserted in cracks in the bark.
In several cases, there were bunches of from 7 to 10, all apparently
busily engaged in sucking the exuding sap, which seemed to
be entirely confined to those deep cracks, and did not spread over
the surface of the bark in any part, so far as could be seen. On
breaking off small bits of bark on the edge of a crack, the bottom
of the crack was seen to be obviously darker in colour, due to a
slight exudation of moisture (sap), which, itself, was also notice-
able. Besides the wasps on the trunk, others could be seen
flying round the trunk and the limb referred to, and but for the
unfavourable weather, there would probably have been more
of them. A noteworthy fact was that, contrary to Mr. Christy's
previous experience, he had seen no hornets on the tree this year,
although several large ones (possibly "queens") had been des-
troyed in the house; and I subsequently took a small nest, with
about a dozen workers and brood, but no queen, from one of
the nesting-boxes for birds which Mr. Christy had put up in the
adjacent wood.
The number of wasps on the tree gradually increased during
succeeding weeks, until Mr. Christy was able to report hundreds
of them sucking or flying round; but still no hornets appeared.
Flies, however, were noticed, and, after dark on one evening,
some moths of several kinds. One of these, which he sent me,
proved to be Noctua xanthographa, an abundant species in late
summer and a very common visitor to the entomologist's sugar
patches.
On the 21st September, Mr. Christy reported that the whole
visitation of sucking insects seemed practically over.
Short of felling or otherwise injuring the tree, I see at present
no feasible way of solving the riddle of the phenomenon in this
particular case. It is to be hoped, however, that the publicity
given to the subject in the Essex Naturalist may lead to the
investigation of other similar occurrences, and publication of
the results in its pages.
Albino Blackbird.—A blackbird, which exhibited uniform
pale-cinnamon colouration frequented the gardens of the Uplands
Estate, Loughton, for several weeks during the spring of 1919,
consorting with normally coloured cock blackbirds.
Percy Thompson.