141 



sticky substance were applied to the under surfaces of the dead 

 branches or other timber used in the construction of such breeding- 

 places, the latter might form traps for the adult flies as well as for the 

 pupae. It is important to note that, in order that artificial breeding- 

 places may have a reasonable chance of success, all known or probable 

 breeding-places must, so far as possible, first be destroyed or rendered 

 useless. 



Range of FligJd. Definite knowledge on this subject is urgently 

 required in connection with G. morsitans. 



The Precise Effects of Clearing. At present we do not know whether 

 clearing actually results in the death of the flies, or merely causes 

 them to migrate. If it w^ere possible in G. morsitans country to find 

 a series of small isolated patches of tsetse, each separated by a different 

 distance (400 yards, half a mile, three-quarters of a mile, and so on) 

 from the next patch of cover, the actual effect of clearing might be 

 ascertained by marking and hberating a large number of G. morsitans 

 in each patch in succession, and then destroying the vegetation and 

 noting the result. If possible, a method of marking which does not 

 m any way impair the activity of the fly should be adopted. The 

 desired end might be attained by collecting large numbers of pupae, 

 and breeding out the flies in cages so arranged that the insects on 

 emerging become permanently marked with coloured powder. 



Systematic Trapping and Catching continued for a considerable jjeriod 

 of time {say, one year). This should be given a thorough trial. In 

 the Island of Principe a marked reduction in the numbers of Glossina 

 palpalis has been effected by catching the flies by means of black 

 cloths smeared with bird-hme and worn by natives. The number 

 thus trapped was 95,000 in the last six months of 1912, or over 500 

 a day. When tried in German East Africa, however, in the case of 

 Glossina morsitans, the method yielded but poor results. It is sug- 

 gested that the failure may be due to the employment on the cloth of 

 some substance which is actually distasteful to the flies and that 

 further experiments with the same substance that is used in Principe 

 would be of value. It is obvious that catching the adults must, 

 relatively at any rate, produce a far greater effect on an exceptionally 

 slow-breeding fly Uke Glossina, than on an insect such as the house-fly, 

 which may produce six hundred eggs at one time. Correct conclusions 

 as to the value of trapping and catching cannot be deduced from a trial 

 lasting only two or three months, in which a handful of natives are 

 engaged ; the value of hmed cloths and of nets in the hands of expert 

 fly-boys should be tested in a selected locality for at least a year, 

 and on a large scale. Some hundreds of natives should be employed 

 in the work, and a corps of, say, a dozen keen and energetic fly-boys 

 should be established in each village in a tsetse area. Payment should 

 be by results, but small rewards would suffice, and the system should 

 therefore prove inexpensive in working. 



Insect Enemies. It is suggested that it might be worth while to 

 attempt the introduction from the southern United States of the 

 minute Hymenopterous (Chalcid) parasites of the genus Spalangia, 

 which have been bred there in large numbers from the puparia of 

 Stomoxys calcitrans, and also attack the pupae of other flies, including 

 Musca domestica and Lyperosia irritans [see this Review, Ser. B, ii, 

 pp. 22-24 1 



