INTERESTING CASE OF INSECT MUTUALISM. I39 



to them from their enemies, but it is certainly a protection to 

 their soft bodies from the heat of the sun — a heat which these 

 nymphs could not survive except for the constant supply of 

 moisture which bathes their bodies and keeps them cool and 

 moist. As soon as the grub or nymph is ready to change into 

 the perfect insect it leaves the froth, which soon dries up, changes 

 its skin for the last time, comes into the possession of fully- 

 developed wings, and moves oiif to enjoy a larger life. The 

 adult insect is a little more than an inch in length. Its upper 

 wings, which are leathery in texture, are coloured yellow with 

 a few black spots or marks, but the colour and markings vary 

 in the same species. 



But now I must mention the fact which justifies the heading 

 or title of this paper. On making a careful examination of a 

 batch of grubs covered with their froth, I noticed a number of 

 small maggot-like grubs, white in colour, and about one-eighth of 

 an inch in length, moving quickly over the moist bodies of the 

 large froth-bearers. The froth had to be removed with a brush 

 before these creatures could be seen. Their bodies were very 

 soft and delicate, and they seemed to be absolutely dependent 

 upon the froth secreted by their huge companions for their 

 safety and existence. But for the protecting froth the hot 

 sun would soon have dried them into dust. Sheltered in this 

 screen of bubbles they found nutriment and protection from 

 ;birds, etc., but especially from the rays of the sun. But what 

 becomes of these little grubs, which are in no sense parasitic 

 upon the frog-hoppers, but only mutuals? When their com- 

 panions mature and fly away there will be no protecting iroth. 

 What then? So soon as the large insects are ready to leave 

 their larval state, or before that time, these tiny " guests " are 

 also ready to be independent of their protection. They pass into 

 the chrysalis stage, and fix to the bark of the tree by a secretion- 

 like varnish their tiny cocoons, which look like minute buds 

 belonging to the twig. These cocoons form ample protection to 

 the life within, and after a short time development takes place, 

 and from the cocoons emerge minute flies, which do not appear 

 to be in any way related to the parasitic flies which abound in 

 this country. Owing- to the loss of material I have not, how- 

 ever, identified these flies, but hope to do so when I get another 

 opportunity. I wish I could tell how the larvae of the little 

 fly are introduced to the frog-hoppers. Probably the parent 

 flies are attracted to the patches of froth and deposit their eggs 

 therein, but this is a point which needs to be observed. There 

 can be no doubt that the minute " guests " are entirely dependent 

 for their existence on the hospitality of the frog-hoppers. It 

 must also be noted that the period necessary for the develop- 

 ment of the larvae of the flies must be sufficiently brief to enable 

 them to complete the change into the pupae before their ho.sts 

 leave the larval stage. If this were not so, they would perish. 

 Taking these points into consideration, we have, I think, a case 

 of mutualism worthv of note and consideration. 



