6 H. W. Peal — Functions of Vaaiform Orifice of Aleurodidse. [No. 1, 



Conclusion. 



The identity of the so-called mercuroxy-ammonium nitrate with 

 dimercnrammonium nitrate is at once apparent. 1 The formation of the 

 "mercuroxy" compound in the presence of strong nitric acid would seem 

 to favour the view already put forward, namely, that the dimercuram- 

 monium compounds are non-oxylic in constitution. Pesci found that 

 when the preparation was washed with hot water, the anhydrous salt, 

 NHg 2 N0 3 was obtained. This, as will be seen, is not, however, borne 

 out by my own experiments. 



I There is, however, this difference that when the compound is obtained by pro- 

 oipitation of mercuric nitrate with ammonia, the colour is faintly yellow. 



The Function of the Vasiform Orifice of the Aleurodidse. — 

 By H. W. Peal, F.E.S. 



The vasiform orifice of the Aleurodidse is a small oval organ always 

 present on the posterior surface of the dorsum of both the larval and 

 adult insects. This organ consists of three parts : The vasiform orifice, 

 which is a more or less oval pit or depression. The operculum, which 

 is a flat shield-like organ which covers the vasiform orifice to a greater or 

 less extent. It is hinged on to the anterior margin of the orifice. The 

 lingula and a narrow tube-like organ, which lies beneath, and some- 

 times projects beyond the operculum. The lingula is usually two jointed. 

 It is continued within the body as a transparent tube, which expands 

 and opens into the body cavity of the insect. 



So far the exact function of the vasiform orifice has received little 

 or no attention and the exact use to which it is put has up to the present 

 been a matter of conjecture. While observers like Maskell have sur- 

 mised that this organ is concerned in the secretion of honey dew, no one 

 as yet has been able to definitely state that such is really the case. 



Some time back, while I was examining an aleurodid which in its 

 earlier stages is remarkably flat and transparent, I was fortunate enough 

 to observe the lingula in motion. This organ was shot out beyond the 

 vasiform orifice with extreme rapidity, it being protruded some four or 

 five times a second. 



When the lingula was shot out the vasiform orifice moved in 

 unison, the upper edge being bent inwards while the whole organ moved 

 candad. The internal opening of the lingula lies directly in the path 



