200 



F. W. DRY. 



3. Not SO much light as could be desired is thrown on the problem of the vicissi- 

 tudes of the two species of parasites in the Kabete field. When we find two species 

 of parasites both attacking the same host we naturally ask why one does not succeed 

 in crowding out the other completely. As it is very unlikely that the resultant 

 of their reactions to the same set of conditions will be precisely the same, we are 

 disposed to look for some condition, not always constant, which affects the two 

 differently. 



Such a condition we did find when it was learnt that the life-cycle of Hadronotus 

 is speeded up more in hotter weather than that of Telenomiis. This, however, does 

 not give us the explanation of the facts from the Kabete field. There it appears 

 that comparative abundance of Antestia eggs results in the proportion of Hadronotus 

 going up, while scarcity of Antestia eggs would seem to send the proportion down. 

 We may make the obvious suggestion that under natural conditions, as in the 

 laboratory, Hadronotus has greater reproductive powers than Telenomus, but that 

 for some reason Telenomus is better able than Hadronotus to find the eggs in times 

 of scarcity. We need, therefore, to know much more about our two species. 



With regard to the effects of temperature, reference may again be made to the 

 almost complete absence of Hadronotus from the several lots of parasites reared 

 from Limuru. The Limuru district, being higher than the Kabete field, is colder, 

 and it may be that it is this condition that gives the advantage to Telenomus. 



VIII. Conclusion. 



The facts so far ascertained have been recorded, together with some hints or 

 suggestions, and this account will have indicated a number of points calling for 

 further inquiry. Reference may be made to the life-history of the parasites within 

 the coffee bug egg, to superparasitism and hyperparasitism, to the effect of laboratory 

 conditions upon the proportions of the sexes of Telenomus, to the behaviour of the 

 parasites, and to a systematic following up of the parasites in a number of plantations. 

 These are some of the lines of work which need to be undertaken to enable us to 

 understand the interactions between Antestia, Hadronotus, and Telenomus. 



Table I. 



Collections of Coffee Bug Eggs from 6-acre Field, Government Farm. Kabete. 



