17 



ASYMMETRY. 



But in certain species the organs of the genitalia are 

 never symmetrical, and where this asymmetry occurs it 

 is as far as I know also constant. I have found this 

 want of symmetry in the harpes and their armature, in 

 the juxta, and in the vinculum. Dr. T. A. Chapman 

 records it also in the penis, (Trans London 

 Entomological Society, Part IV., 1902), but for my own 

 part I fail to see how a single organ, especially when it 

 is cylindrical and curved, can be spoken of as 

 asymmetrical. 



It is a noticeable fact that this want of symmetry 

 appears to affect particular genera, and even groups. 



MATERIAL USED. 



Where I had no reason to doubt a species, I have 

 made the drawing from a single specimen, but in the 

 majority of cases two or more specimens have been 

 examined for verification ; and in the case of the 

 Hydrcecia nictitans group close on 100 examples were 

 prepared, before satisfactory evidence could be produced 

 of the existence of several species, amongst insects 

 which had previously been popularly considered one ; 

 confirming Mr. Tutt's suggestions of 20 years ago. 



Care must be taken that the correct bodies are on 

 the specimens before they are prepared. It is a common 

 failing with collectors, rather than have a specimen in 

 their cabinet without a body, to glue on the body of any 

 species that first comes to hand. I need hardly say 

 that, to the genitalia worker, this is productive of much 

 unhappiness. It is also well to examine the frenulum 

 for the sex, before detaching the insect's body. 



AS MICROSCOPICAL OBJECTS. 



The examination of these parts is most interesting 

 and often at times exciting. The marvellous variety 



