AN INTERESTING CASE OF INSECT MUTUALISM. 



By Rev. Nendick Abraham, F.R.M.S. 



By the term "mutualism" as distinct from "commensalism" or 

 "parasitism," we mean such cases where two distinct and unrelated 

 creatures are found constantly in close association without any 

 cost or loss to either, though in some cases there may be some 

 gain to one of the partners derived by the connection. 



I will now set forth a case of mutualism which came under 

 my notice while living in Durban, Natal. One of the partners 

 is deserving of some special attention for its own sake, and 

 though its habits are generally well known, I will refer to them, 

 as I have had opportunities for careful observations. The insect 

 belongs to the family Cercopidse, and is one of the " frog- 

 hoppers " or " spittle bugs," and is known to entomologists as 

 Ptyclus flavescens. There are several well-known species of 

 frog-hoppers in this country, such as Aphrophora grossa, com- 

 mon in peach trees. The insect I am to deal with is perhaps the 

 largest of the family, measuring over an inch in length. It is 

 found in Natal and neighbouring parts of this country. In com- 

 mon with other members related to it, it does not pass through 

 a complete metamorphosis. The only striking difference, apart 

 from size, between its infant and adult condition is that in the 

 latter it has acquired two pairs of wings. In its grub or nymph 

 stage the insect covers itself with a quantity of froth, which 

 (|uite hides the creature from sight. This froth is obtained and 

 manufactured in the following manner. The mouth-parts of 

 the frog-hoppers are iashioned into a long, sharp beak, which 

 is thrust into tender shoots of plants or soft bark of trees, and 

 is employed in sucking up the sap. If one of the grubs be re- 

 moved from its covering of froth and placed on a clear place on 

 a twig of the tree, it will be noticed that the beak will presently 

 be made to pierce the bark, and the sucking operation com- 

 menced. In a short time there will be a discharge of clear fluid 

 from the posterior end of the body, which will soon flow under 

 and over it. After the lapse of a little time the creature will 

 commence an active movement of its abdomen, or the hinder 

 segments of it. The movement is up and down, and from side 

 to side. With each downward stroke it carries into the fluid a 

 minute |X)rtion of air, which becomes entangled by the viscosity 

 of the fluid, and so forms a tiny bubble. A continuation of the 

 movements soon turns the fluid into a quantity of froth, which 

 completely covers the nymph. The sucking process continues, 

 and in the case before us such a surplus of fluid passes through 

 the body of the insects that it freely drops from the tree, as 

 though some secret power caused the tree to drip rain. This 

 fact is the ori»in of the fabled " rain-trees," which someone 

 proposed should be planted in desert places to make up for the 

 absence of rainfall. The truth is strance enough without the 

 need of exaggeration, as the following obsen'ations will prove. 



