+
2. Pulex Cheopis, Roth.
22
Found upon rats in Ashanti and at Accra.
3. Ctenocephalus serraticeps.
Found on dogs.
1. Dermanyssus, sp. nov.
Gamasida.
Found in cavity of first abdominal segment of the large black bee
(Xylocopa).
2. Dermanyssus, sp. nov.
Found in fur of the striped mouse (Mus Barbarus).
Hydrachnidæ.
Specimens of this family were frequently observed upon Culicidæ, Empidæ,
Coleoptera, and Orthoptera.
Hemimerus talpöides, Walker.
Orthoptera.
This parasitic orthopteron was found in large numbers in the fur of the large rat (Cricetomys Gambianus, Waterhouse), both in Ashanti and at Accra.
23
Such statements occasionally prompt useful investigation, but are generally
valueless.
9. That it is of importance to ascertain and record the native names of insects, and that dictionaries not compiled by entomologists cannot be relied upon for correct information. The native name should be ascertained by showing the insect in its resting attitude to intelligent natives of the district where it has been caught, and before accepting the word, it should be used for making enquiries about the insect,. so that certainty that it is at least a generic name may be gained. Suppose, for example, that a tsetse fly be shown to a native, and he calls it by the word in his language for biting-fly; now this word can be applied to all the biting flies, and, as natives usually make no clear distinction between biting and stinging, to many of the wasps and bees also. It is, therefore, useless for the future identification of even the family of the insect to which it is applied.
10. Photographic Methods.-These diptera were photographed as soon after setting as the legs and wings had dried sufficiently to retain their set position.
The photographs were all taken with a Zeiss microplanar lens of 100 mm. Eq. Focus, upon Messrs. Wratten and Wainwright's panchromatic plates.
In almost all the photographs, a Wratten six times yellow screen was used, attached to the back of the lens tube. The lighting of the specimens was effected by the use of three mirrors-one at an angle of 450 below and one upon each side of the insect.
W. M. GRAHAM, M.B.,
Medical Officer, West African Medical Staff,
Gold Coast.
r
London,
13 January, 1909.
Some Supplementary Remarks.
During my entomological work in Ashanti, certain general propositions have been forcibly suggested to me by experience. I place them on record here as they may perhaps prove an aid to future observers.
1. That it is an impossible task to collect only the blood-sucking diptera. Were the dipterous fauna of West Africa known, it might be possible for an expert to single out these flies, but as this fauna is only beginning to be studied it is at present impossible to do so, and, in order that the blood-sucker may be secured, a general collection of all the diptera must be made.
2. That many of the diptera which do not suck blood are of very great economic interest.
3. That it is of great importance to observe the complete cycle of 12 months with the succession of insects accompanying the meteorological changes.
It should be remembered that some species of insects in each locality have special periods of seasonal prevalence, sometimes of short duration.
4. That a knowledge of the exact geographical distribution of insects would be of great value, for should it be shown that the geographical distribution of an insect and of a disease were conterminous, the direction in which further investiga. tion might be fruitful would be suggested, and if, in addition, the seasonal pre- valence were found to be synchronous, the indication would be made still more clear.
5. That a travelling observer is, necessarily, unable to ascertain the geogra- phical distribution of those insects that have a short seasonal prevalence. This can be ascertained only by an observer who resides a complete 12 months in the locality.
6. That printed descriptions of diptera are useless to any but trained entomo- logists. That there is need, therefore, of a set of pictures which could be used for the identification of specimens by unskilled observers. The usefulness of such a set of pictures might be supplemented by a list of the known African species of each family, and, where possible, by tables of genera and species.
7. That specimens of diptera collected by untrained persons are usually of very little value. They are broken, or damaged by mould, mites, or ants, and cannot be identified with certainty. None of the specimens of diptera sent me in 1907 arrived in good enough condition to be photographed; and those infected with moulds or vermin could not be placed in the collection as they would have infected the perfect specimens.
8. That statements regarding the habits of insects made by natives should always be listened to attentively, but very strictly scrutinised before acceptance.
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Reference :-
TPIC.O. 885
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ALLY WITHOUT PERMISSION OF THE BE REPRODUCED PHOTOGRAPHIC- COPYRIGHT PHOTOGRAPH-NOT TO
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