116 



wait for their prey and then leap upon it. 1 Of course Tsetse-flies are 

 not the only insects attacked by these spiders. 



Dr. J. J. Simpson (142.1.), in his account of entomological researches 

 made by him in the Gambia in 1911, writes : " As already noted, I 

 observed in the Government steamer an Attid spider [Plexippus 

 paykulli, And.] attack and kill numerous tsetse, and this species of 

 spider seemed to show a distinct predilection for G. palpalis, although 

 several other species of Diptera were almost equally abundant. It is 

 very doubtful if this is of actual importance, but, as a fact in the 

 bionomics of tsetse, may be recorded here." 



Carpenter (26), writing with reference to G. palpalis in islands in 

 Lake Victoria, Uganda, thinks it probable that certain spiders have 

 been responsible for considerable diminution in the numbers of flies, 

 where conditions are apparently favourable for their increase. 



Swynnerton (145), in his paper relating to conditions in North 

 Mossurise, Portuguese East Africa, says : " Spiders of various bark- 

 haunting species that hide in crannies and leap on their prey accounted 

 for a number of the flies I had under observation in the net [vide supra, 

 p. 71], and it is probable that these are the female tsetse's most 

 important enemy. One tsetse (morsitans) was seen caught in the net 

 of a web-making spider." 



Fiske (54) notes " the incredible number of spiders that occur locally 

 at points along the mainland shore, or on small islets " in Lake Victoria, 

 Uganda. This peculiarly competent investigator, in addition to 

 recording the catches of various insects entangled in the snares of a 

 gigantic web-spinning spider (Nephele pilipes), which is particularly 

 abundant in certain of the localities mentioned, also furnishes com- 

 parative statistics showing the average infestation by G. palpalis of 

 islands with no spiders and with many spiders respectively. From the 

 evidence thus obtained, Fiske thinks.it "extremely probable that 

 where infestation by spider is excessively heavy it must have some 

 effect in reducing local density of tsetse " ; he also considers that 

 certain islands " noted .... as very lightly or not at all 

 infested, may possibly owe freedom from fly to infestation by spiders, 

 which was fairly heavy in each case, as well as to absence of breeding 

 grounds." After writing of dragonflies (see p. 118), the probable 

 effect of which in reducing the numbers of G. palpalis in various islands 

 or districts is also acknowledged, Fiske adds : " Apart from spiders 

 and dragonflies, no destructive enemies of tsetse have been observed 

 that appeared to be specifically responsible for appreciable reduction 

 in density of Glossina palpalis." 



Predacious Insects. The small number of insects recorded up to the 

 present as preying upon Tsetse-flies belong to the Orders Diptera, 

 Hymenoptera and Neuroptera. Writing with reference to G. morsitans 

 in the Luangwa Valley, Northern Rhodesia, Mr. LI. Lloyd says (88) : 

 " An Asilid fly was taken on the wall of the laboratory devouring a 

 tsetse-fly ; it had made a wound in the side of the thorax. The 

 favourite food of these rapacious insects seems to be Tabanidae, 

 especially the larger species. One was taken eating a dragonfly. 



1 The Family Salticidae includes a large number of species, which are almost 

 always of small size ; they are roving creatures, spinning no webs, but lying 

 in wait and springing suddenly upon their prey. In the majority of cases the 

 tropical species exhibit magnificent colouring ; the males are often more brightly 

 coloured than the females, and the quaint behaviour of the former, in search of 

 the opposite sex with a view to pairing, is frequently very curious. 





