BLOOD GILLS OF SIMULIUM PICTIPES 



THOMAS J. HEADLEE 



It is a well known fact that during larval life many aquatic in- 

 sects possess gills. These have been regarded as thin transpar- 

 ent extensions of the body wall, which may or may not contain 

 trachefE. In one type of insect gill, the organ is abundantly sup- 

 plied with trachese, and the evident function of the organ is the 

 purification of the air contained in the traclicu'. Such a gill is 

 known as a tracheal gill. In tlie other type, known as a blood 

 gill, it is blood within the gill that is purified. 



Whether there exist in pterygote insects true blood gills in the 

 narrow application of this definition, is still an open question. 

 Such organs have been described as present in many groups, not- 

 ably in the ]ar\a' (^f I'richoptera and Diptera. Those interested 

 in the general dis< ns>ion of the subject may find a concise but 

 excellent n snmi oi' the \v..rk done in Kolbe ('93) and Packard ('98). 



Few of thest> s(. calh'd blood gills have, however, been subjected 

 to niorj)hologieal examination. It is the purpose of the present 

 paj)er to discuss from this vie\v-i)oint these structures of the larva 

 of Simtdlinn piciipes Ilagen. a species of black-fly abundant in 

 the streams about Ithaca, New "S'ork, l>ut 1 shall first consider 

 some of their grosser variations which ap|)ear in other specie> of 

 Simulium. 



