The Microscope and Biology. By W. Wesche'. 405 



or feathered, to enable the male to maintain a firm hold of the 

 female. In the Culicidre even the claws of one pair of legs are 

 altered, and have an extra barb. On the under side of the abdo- 

 men are bunches of hair, tubercles, and spined areas in regions of 

 contact. 



As in the raptorial Ephydridse, so in a few insects in this 

 section, the femur itself is modified into teeth and hooks. The 

 genera Hydrotea and Borborus nitidus Mg. among the flies, are of 

 this rarer type. Even the sucker has been used, and most 

 microscopists are familiar with the beautiful apparatus on the fore 

 legs of the Dytiscus Beetle. The stridulating organs used in 

 calling the sexes together, would come under this head also. 



In the female, secondary sexual characters are comparatively 

 rare, and mostly consist of arrangements of spines on contact 

 areas. 



I only know of one modification of the limbs, and that con- 

 sists of enlargement of the last joint of the hind tarsi, and I would 

 feel inclined to place this in another section, were it not for the 

 fact that the males are without this character.* 



As this division of the subject has had but little attention, I 

 will give an account of my observations, which, however, are con- 

 fined, as will be most of my remarks, to insects of the order Diptera. 



Secondary Sexual Characters in the Female Insect. 



Bibionid^e. Dilophus febrilis L. has two hairy tubercles on the 

 posterior ends of the eighth segment, laterally placed. The male 

 also has two on the ventral side of the abdomen. Both sexes 

 have two rows of teeth, or strong hairs modified into teeth, across 

 the thorax. Their presence in the female is easy to understand ; 

 in the male, especially as they seem nearly as well developed as in 

 the female, difficult. 



Chtronomyid^. — Chironomus plumosus L. is provided with two 

 patches of soft hair on the dorsal sides of the last segment. 



Empid^e. — In Hilara cilipes Mg. there is a notched guide for 

 the fiagellum of the male on the ovipositor of the female. 



DoLiCHOPODiDyE. — A large number of species in the Dolicho- 

 podida? have a strong blunt fringe of spines on the end of the 

 ovipositor. This is a character that so far I have only found in this 

 family, which is so remarkable for the development of primary 

 characters in the male. The antennae are also often smaller than 

 those of the male : the reason is obvious. 



* The late Dr. Meade iu his British Anthomyidae, p. 47, gives Chortophila 

 billbcrgi Ztt. as another example, the female having the second and third joints 

 of the front tarsi dilated. Drs. Schiner and Zetterstedt are mentioned as having 

 wrongly ascribed this character to the male. I am not acquainted with the 

 insect, and cannot say which doctor is right. 



