191 



country we have no malaria anywhere and because, as far as we know, A. maculi- 

 pennis is spread over the whole country almost in an equally large number. If now 

 we compare the results of ROUBAUD'S investigations on the life-history of A. maculi- 

 pennis with mine, we shall find great coincidence. 



. He calls attention to the enormous amounts of Anophelines on the ceiling and 

 walls of the stables; they are rare in houses which are not inhabited by man or 

 cattle; here we only find some males; in the stables they originally only sought 

 shelter; now they also look for nutriment there. Even in houses which only con- 

 tain the stable and a single room for the inhabitants, almost all the mosquitoes are 

 to be found in the stables; there are none or only a very few in the room. Man 

 is not attacked by the mosquitoes; they only suck blood upon the domestic ani- 

 mals; the few mosquitoes which can be caught in the dwelling rooms have almost 

 always empty stomachs, those in the stables are almost always blood-filled (never 

 any less than 40 % and often over 90 %). In all these main points there is full 

 accordance between the statements of ROUBAUD and myself; it must only be remem- 

 bered that ROUBAUD has only studied the biology during summer and not like my- 

 self followed the life- history the whole year round. His indications that the Ano- 

 phelines do not occur in non-inhabited rooms are most probably only correct for 

 the time he has studied the mosquitoes; at all events in our country the Anophe- 

 lines entirely disappear from stables and inhabited rooms in the six winter months, 

 the hibernation taking place exactly in outhouses, unoccupied rooms; the presumed 

 cause is indicated on p. 164. 



The most striking difference between ROUBAUD'S and my results is that the 

 Anophelines of Vendee are very active animals out of doors. However favourable 

 the conditions for nutrition may be on the spot where the female has spent the 

 period of daily rest, this is always abandoned for flight in the open air at night, so 

 that a new host must always be found for the meal before the next day's rest. The 

 Anopheline-population of any given shelter is therefore entirely or almost entirely 

 renewed every night. If therefore all the Anophelines present in a certain building 

 were captured and destroyed several days in succession, provided that the host 

 conditions are favourable, the numbers would be constantly replaced, probably 

 without any noticeable modification of the total. It has been proved by marking 

 some thousand individuals that the Anopheline fauna of any given spot, however 

 densely populated it may be, is entirely renewed within a few days; the regu- 

 lar flight in the open directly observed during night by ROUBAUD has been proved 

 to be indispensable to the life of A. maculipennis. It will be understood that ROU- 

 BAUD and I have arrived at quite opposite results upon this point; in Vendee 

 the Anophelines are on the wing every night during the summer, in Denmark 

 hardly ever, and only for mating and egg-laying processes ; I have hardly ever caught 

 an A. maculipennis out of doors. I am sure that both our observations for each 

 country are quite correct. The Anophelines of Vendee and Denmark differ from each 



