202 BBITISH TYROGLYPHIM. 



as tubers, tap-roots, etc. I have very frequently 

 watched H. rostro-serratum, and other species, feeding. 

 The process has always been as follows : The mandibles 

 are darted out alternately and rapidly, one mandible 

 being withdrawn while the other is being exerted; 

 thus they are alternately plunged into the substance to 

 be fed upon and withdrawn from it, and by a saw-like 

 action cut the vegetable cell- walls and allow the con- 

 tents to escape. While the mandibles are at work the 

 anterior of the two palpal flagella, which is usually 

 much the longer, beats regularly and strongly, causing 

 a current which carries the contents of the torn cells, 

 as it exudes, to flow steadily into the open mouth of 

 the creature, into which it is generally guided by a 

 short wide funnel formed by the membrane attached to 

 the two palpi, and sometimes to the maxillary lip. 

 The Acarus keeps slowly advancing as its mandibles 

 empty the food material before it. Megnin was of 

 opinion that these Acari were the initiators of decay in 

 fungi; he even went so far as to suggest that fungi 

 would probably not decay without them. I am not 

 able to agree with him on this point ; it seems to me 

 that they are followers of decay ; I have not ever 

 found them, as I have so frequently found Rhizoglyplms, 

 eating into the sound portion of a root ; and if placed 

 in such a situation, or upon sound, healthy, suitable 

 vegetation, they do not appear to me to attack it as 

 Rkizoglyphus does ; they do not thrive until the plant is 

 wounded, or fungoid growth, nematoid worms, other 

 Acari, or some cause has started decay. In the species 

 which live in the exuded sap of trees the action of the 

 mandibles is not so noticeable. This exceptional mouth 

 may possibly be considered to be an adaptation to the 

 mode of life of the genus ; but it is not found in Hericia, 

 which wades in the exuded sap of trees, and feeds 

 upon it exactly as some species of Histiostoma do. 



The Kostrum in most species is clearly defined, and 

 is apt to be somewhat square or oblong ; this form is 

 given by the size and importance of the maxillary lip 



