Proceedings, l!)l;l 7 



out a whole mass of fine threads and fastens the fly to its hist rosthi^-placo. From 

 a layer of fungus-threads all over the body of the fly thousands of these minute 

 spores are again shot into the atmosphere, until all the food substance in the fly is 

 exhausted. 



Some of you may have seen a dead fly on the window-pane with a halo of white 

 around it ; this halo is composed of the many threads of fungus-hyphfe fixing the 

 fly to the glass, while it liberates its spores. 



I presume that most of those present have reared larvfe of Lepidoptera. Have 

 you ever found that some of those larvfe which pupate in soil did not go through 

 their whole metamorphosis, but died in the pupa stage; that on the pupa a white 

 coat appeared accompanied by minute outgrowths? This is another plant Icnown 

 as Isarin, whose spores are found in some soils. The larva when attacked is usually 

 not killed until after it has pupated. 



There are other insect-diseases of equal interest; perhaps the most curious one 

 is what has been popularly termed the " vegetable caterpillar." This, it is explained. 

 is an organism which at one stage of its life is actually a creeping caterpillar, and 

 at another stage is a plant, having a root in the ground and a stem bearing fruits 

 above the ground. 



This marvellous creation is in reality a caterpillar attacked by a disease known 

 as Cordi/ccps militaris, a fungus closely allied to Claviceps (the ergot-disease of 

 grasses). In this case, however, the fungus fills up all the available space inside 

 the caterpillar without destroying the vital organs, and the caterpillar grows to 

 practically its full size. When it descends into the soil to pupate, the fungus kills 

 It, and proceeds to absorb all the remaining food material. This results in the whole 

 interior h^ing filled by a hard woody substance composed of fungus-threads. 



Later on, from one end of what was a caterpillar, a stem-like structure grows 

 to a few inches above the surface of the ground, and this bears thousands of spores 

 which lie about, or are blown from place to place, infecting other larvre. 



This i>articular species of Cordyceps is common in New Zealand, but is found, 

 along with several other species, in North America. 



P.\EASiTiSM V. Introduction of Disease. 



We have heard a good deal about parasitism as a means of combating orchard 

 pests, but I am always sceptical as to the ultimate result of introducing new species 

 of animals into a country, and more particularly when you introduce one lot to get 

 rid of another. 



By introducing other insects, you are introducing the food of other animals 

 which prey on these. There is a risk of nature restoring the balance by the increase 

 of insectivorous birds, and, as Is well known, birds are recognized agents in spread- 

 ing disease and insect pests, so that we may ultimately find ourselves worse in the 

 end than we were at the beginning. 



As I already mentioned, the majority of our most dreaded contagious diseases 

 belong to the vegetable kingdom. It would be interesting to see what could bo done 

 in introducing parasitic fungi to combat insect pests. The introduction of disease 

 amongst rats has been responsible for great havoc in reducing their numbers, and 

 we may yet be able to treat our insect pests in a like manner. 



Friendship between Plants and Insects. 



In the mid.st of the battle between plants and insects, let us not forget that there 

 are many friendships. There is some good business transacted between the two 

 kingdoms. I need only refer to the arrangenieut existing between certain insects 

 and certain flowers, whereby the insect acts as a pollen-bearer in return for the 

 nectar w-hich the flower provides. 



I cannot possibly enter into the various schemes, devices, and dodges adopted by 

 flowers to attract certain insects and keep out others; this would take several days. 



