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PUBLIC RECORD OFFICE

Reference :-

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PUBLIC RECORD OFFICE, LONDON

ALLY WITHOUT PERMISSION OF THE BE REPRODUCED PHOTOGRAPHIC-

COPYRIGHT PHOTOGRAPH-NOT TO

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During the first part of this period the daily catches were segregated in separate cages containing a few inches of sand. At fairly frequent intervals the cages were overhauled and the active Earwig contents were transferred to a new cage, so that the sand could be sifted to locate any parasites. On such days as the overhauling took place no collecting was done.

Collections were made on Rothamsted Farm mostly, but, in the hope that a higher percentage of parasitism might be obtained visits were also made to the New Forest at Brockenhurst, Osterley Park, Epping Forest and Theydon Bois, and Wimbledon Common in the vicinity of Beverley Brook.

The first Tachinid puparia bred out from the Earwigs collected were found on 13th September in the cage containing the first day's capture. Subsequently others were found in the various cages up to 17th November.

One lot of puparia-121 in all-were packed in sphagnum moss in five boxes and sent to London on 15th November for shipment. The next lot consisted of no more than 12 puparia, and were sent off on 5th December.

The total number of Earwigs collected from the beginning of the work to the end of November, was 10,451. This figure, therefore, gives a total percentage of parasitism of only 1301 per cent. But it would appear that the work was started too late in the year, for the first day's capture of only 155 Earwigs gave a parasitism of 7741 per cent.; the second day's capture with only 115 Earwigs gave 5173 per cent parasitism; and from then onwards the percentage of each cage gradually dwindled to nothing. The collection made at the New Forest on 19th to 21st September of 874 Earwigs produced 30 Tachinid puparia, giving a parasitism of 3.432 per cent. Whereas another collection made at Rothamsted in early November of 882 Earwigs has failed to produce a single parasite.

From an examination of the collection of these Tachinids in the British Museum it is evident that their period of greatest activity is from late Spring to late Summer, consequently the highest percentage of parasitism must obtain during the Summer and early Autumn, as the evidence is that the parasitic larvæ grow rapidly within their hosts.

With regard to the parasites, it is evident that species of Digonochaeta pre- dominated, but another species has been obtained-so far unidentified.

About 120 puparia of the Digonochaeta appearance were collected in the field, and from observations there, and tests and examinations in the laboratory, the Tachinid parasites in the oven are found to be subiected to a fairly heavy hyper- parasitism. Amongst the hyperparasites is a Chalcid. Dibrachys cavus, a pupal parasite, whose various stages are now worked out. There are possibly others of the same family. A Braconid or Ichneumon has also been found, but not bred through yet-its life history is unknown.

Gregarines and nematodes have been found in the Earwigs.

The Pear Slug-Worm.

A large number of these larve estimated at 1,700-were phtained in an orchard near Worthing on 22nd September. They were put up

into 34 soil and foliage.

with cages

Through an omission, the larva that died before pupating were not saved so the mortality is only approximately known.

Within a fortnight after their arrival many larvæ had pupated. The appear- ance of a full-grown larva at this time led to the discovery of the presence of the eggs of a parasite within it. And subsequently to that occasion many others

similarly parasitised were observed.

By early December it was apparent that the parasites were hibernating as embryonic larve. It was therefore decided to ship the hibernating slug-worms in their cocoons so that their development, and that of their parasites, could be hastened in New Zealand in order that the latter should be in time for the work they were destined for.

On 29th December 400 cocoons were packed in sphagnum moss in boxes and sent. to London for shipment. On 9th January 850 cocoons were sent to London. The remainder-120-were retained.

From dissections made of fifty slug-worm larvæ it became evident that the per- centage of parasitism was high, only five unparasitised specimens were found, i.e., 90 per cent. parasitism. At this rate it is conjectured that at least 1,000 of these parasites have been shipped to New Zealand.

From the remainder of the cocoons retained an attempt is being made to work out the life history of the parasites-under natural conditions. The variation

157

observed in the eggs suggests that more than one species of parasite is present, and they are probably Ichneumons. So far, however, their development has not pro- gressed beyond the first stage larva, but observations are being continued.

B. LABORATORY WORK.

The collection of material for microscopic study has been in progress from the commencement of the work. And during February and up to the time of writing in March the descriptions of the parasites and their biology are being carried out, with a view to publication.

A. D. IMMS,

28th March, 1923.

20002

SIR,

No. 51.

COLONIAL OFFICE to FOREIGN OFFICE AND BRITISH SOUTH AFRICA COMPANY.

WITH reference to the letter from this Department of the 20th of December,

Downing Street, 11th May, 1923. 1921,* I am directed by the Duke of Devonshire to transmit to you, for the infor- mation of [the Marquess Curzon of Kedleston,] [your Directors,] the enclosed copy of a despatch which is being sent to the Officers Administering the Governments of the West and East African Dependencies relative to Tsetse Fly investigations .in Africa.

2. The Secretary of State thinks that it would be interesting to [the Govern ment of the Sudan] [the Administrators of Northern and Southern Rhodesia] to know what work has been carried on in other parts of Africa during the years 41921 and 1922, and he feels sure that if they desire fuller particulars with regard to the work in any of the Dependencies concerned, the local Government, or the Director of the Imperial Bureau of Entomology, will be glad to supply them.

I am, &c.,

H. J. READ:

20002

No. 52.

THE SECRETARY OF STATE to THE OFFICERS ADMINISTERING THE

(Nigeria.

(Gold Coast.

(Sierra Leone.

Gambia.

(Kenya.

(Uganda.

(Zanzibar.

(Nyasaland.

(Tanganyika.

GOVERNMENTS.

Miscellaneous.)

Downing Street, 11th May, 1923.

SIR,

WITH reference to my predecessor's Miscellaneous despatch of the 20th of December, 1921, I have the honour to transmit to you, for your information, the enclosed copy of a Memorandum which has been prepared by the Director of the Imperial Bureau of Entomology on investigations into the Bionomics of Tsetse Flies during the years 1921 and 1922. The Memorandum is only a bare summary of the work which has been done, but it will no doubt be of interest to your Government to know the lines on which investigations have been carried out in different parts of Africa, and I feel sure that if fuller particulars of the work conducted in other parts of Africa are desired, either the Government concerned or the Director of the Bureau will be glad to supply them.

2. The possibility of a general scheme for extended Tsetse Fly investigation in Africa on a large scale must still, I fear, be regarded as remote, as the question of finance presents great difficulties. At the same time, it is most desirable that work of this kind should be carried on individually by different Governments so far as resources permit, and I think that you will agree that the position indicated by Dr. Marshall's Memorandum is most encouraging.

* No. 37: .t No. 52.. ‡ No. 38.