18 BEHAVIOUR AT NIGHT. 



belongs to a species * with habits somewhat different from those 



of Gloasina morsitam and the other better-known forms. 



The Tsetse apnears to pass the night I'fistine 

 Behaviour at night. . , , , n u u 



either on the ground or on the smaller branches 



of bushes and trees, f and although there is a wide-spread belief 



that during the hours of darkness fly-belts may be crossed with 



impunity, there is abundant evidence to show that this is not 



invariably the case. A moonlight night during the South African 



winter may be safe enough, J but at other seasons and in more 



tropical latitudes it is well to wait until the temperature of the 



air has fallen sufficiently to render the insects sluggish. Brad- 



shaw [77] states that the Tsetse bites " during part of the night, 



if warm," adding, " J consider it dangerous to travel at night with 



cattle and horses, until it begins to grow cold towards the middle 



of the night, as I have been bitten often until past 11 p.m." 



Selous [76] describes a moonlight tramp along the Chobe River, 



when the Tsetse " kept flying up from the ground on to my 



naked legs, and bit as fui-iously as in the daytime " ; and Captain 



Crawshay, writing of his experience of Tsetse-flies in Nyasaland, 



agrees that they bite at night as well as by day, when the moon 



is bi"ight.§ On the other hand. Kirk [28] writes : " By night 



I have never been bitten by Tsetse, nor do they fly about after 



sunset" ; and Bruce |] says that he has "not noticed them 



biting during the night. ..." These discrepancies, however, are 



no doubt due to differences in locality, temperature, and other 



conditions. Captain A. St. H. Gibbons [152], writing of his 



experience of Tsetse on the Njoko River, Northern Rhodesia, 



in Augu.st 1895, says: "At night the danger is very small, 



though it is a mistake to imagine that the Tsetse keeps such 



early hours as other flies. I have at times been worried by 



them an hour after the sun has gone down, and have known 



flies to buzz into my tent as late as 9 o'clock on a dark night 



* Perhaps Glossina longipenniR, Corti. 



t Dr. Holub [no] draws attention to the risk incurred b}' croesing at 

 night "certain thickly-wooded laterite knolls," in the vicinity of the 

 Zambesi, which happen to be infested by Tsetse, since owing to the narrow- 

 ness of the track it is impossible to prevent the waggons from brushing 

 bhe flies from the twigs and carrying them along. 



X Cj. C. J. Andersson, [20]. 



§ Cf. Chapter VII., Appendix B, p. 288. Sir Harry Johnston's advice 

 [14^ that, " if a Tsetse-haunted district must be crossed, it should be 

 done at night-time — by moonlight if possible," should therefore be received 

 with caution. According to Eaines [55], a "dark and cloudy " night is 

 safest. 



II Cf. Chapter VII., Appendix A, p. 272. 



