( 15) 
IV. BIONOMICS OF THE CULICID^ IN FREETOWN. 
II. Differences between Culex and Anopheles.— Our next duty was to study the 
habits of the inculpated Anopheles with reference to the prevention of gnat-fever. We propose to 
give our bionomical observations here,* and to reserve a description of the insects themselves for 
the Addenda. 
In view of the particular connection which seems to exist between Anophela and gnat- 
fever, it is important to possess information sufficiently simple to enable anyone to distinguish 
between them and the common gnats of genus Culex. Such points of difference have alrcad)- 
been recorded by one of us as the result of his observations in India [14] ; and we were able to 
assure ourselves that the same differences hold also in Freetown. 
(i). Adults. — The principal zoological dis- 
tinction between Anopheles and Culex is that the 
palpi of the female are long in the former and short 
in the latter. But this is of little assistance to those 
who are not entomologists, and who may not know 
what the palpi are. Fortunately there is a more 
striking difference — one which can be perceived by 
anyone at a glance — in the attitude adopted by the 
respective insects when seated on a wall. In 
^ 3. AnophcU^ an. I Cuhx. 
Anopheles the axis of the body is almost vertical to 
the wall ; in Culex it is parallel to the wall. Popularly put, the Anopheles may be said to stand 
on its head, with the point of its tail projecting outward ; while the tail of Culex points downward, 
or even a little toward the wall. 
Another noteworthy point of difference is the general shape of the body. In Anopheles the 
head and thorax are comparatively small, while the long palpi are held in contact with the 
proboscis. This gives the insect a peculiarly elegant fusiform shape —like that of a humming-bird 
moth ; while the proboscis looks like a long thick beak. On the other hand, Culex has a thick 
ungainly thorax, and a thin bare proboscis. In siiort, tlie appearance of Anopheles suggests that it 
can fly further and more rapidly than Culex. 
Thirdly, the wings of Anopheles are generally spotted along the anterior edge (to use popular 
* It should be clearly understood that our remarks apply only to our own observations. We cannot answer for facts 
in other localities. 
