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Abstract. The payload of the Italian/Dutch spacecraft BeppoSAX includes a set of four X-ray concentrators each of geometric area 124 cm 2 together with imaging gas scintillation proportional counter detectors located at the focal planes. One of these detectors, the Low-Energy Concentrator Spectrometer (LECS), is sensitive to X-rays in the energy range 0.1 − 10 keV, while the other three cover a narrower energy range of 1.3 − 10 keV. In order to achieve the extended low-energy response of the LECS a novel type of gas scintillation proportional counter has been developed which dispenses with the separate drift and scintillation regions of conventional instruments. The design and performance of the instrument together with its calibration and data analysis system are described here.

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SUMMARY To investigate the failure of DDT to interrupt malaria transmission in parts of the British Solomon Islands Protectorate, regular all‐night man‐biting catches of malaria vectors were made before and after DDT house spraying on San Cristobal Island. Changes were observed in the man‐biting behaviour of Anopheles farauti. There was a reduction in the degree of entry into houses and a shifting of the times of peak biting. Whereas before spraying the indoor and outdoor biting cycles differed, after spraying there was no difference although both the indoor and outdoor cycles had altered. DDT was found to have a deterrent effect on An.farauti but this effect decreased with time. DDT also appears to eliminate a dominant indoor feeding fraction of the farauti population. Following this there can be an increase in an outdoor feeding fraction which can be responsible for a resumption of malaria transmission. Biting cycles obtained before spraying are also shown for An.koliensis and An.punctulatus.

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