THE VICTORIAN NATURALIST. Ill 



Hepialus virescens (Roberts). This caterpillar feeds on the leaves 

 of the Rata ( Metrosideros ), and is also stated by Hamilton* to 

 be found on the Papa Narau (Coprosma grandiflora). When its 

 time for assuming the chrysalid state arrives, the caterpillar 

 buries itself in the ground, and up to the time of its doing so no 

 signs of anything out of the common have been observed, 

 though this is probably due to want of observation, and is a 

 subject deserving attention. 



The first indication of what has taken place, which we have, is 

 the appearance of the spear-like processes, which are the stipes 

 or bearers of the spore-cases of the fungus, and on digging it up 

 we find that no attempt to assume the chrysalid state has been 

 made. On examination we find that the whole of the internal 

 organs of the caterpillar have disappeared, and have been 

 replaced with a dense mass of mycelium resembling in structure 

 some of the dense corky species of fungi, and consisting of a 

 dense body of mycelium. It becomes now quite evident that 

 the fungus has flourished at the expense of the caterpillar, 

 utilizing the organs of the insect for its own nourishment. Since 

 the parasite was first named, by Berkeley, Cordyceps robertsii 

 (Berk.), a good deal of change has been made in the classifica- 

 tion of the genus, and the individual under consideration was 

 classed as a Sphseria, but is now, I understand, definitely 

 relegated to the genus Isaria, and so should properly be called 

 Isaria robertsii (Berk.) 



The mode in which the caterpillar becomes infected with the 

 spores of the fungus has not been exactly observed. It has been 

 suggested by some that the spores are eaten by the caterpillar 

 adhering to the leaves on which it feeds; by others, that the 

 spores enter by the spiracles ; and by others, that the insect 

 becomes infected while burying itself to undergo its metamor- 

 phosis, the spores being mixed with the earth. 



An examination of the specimens which I exhibit to-night shows 

 that there is considerable variation in the size of the caterpillars 

 and in the length of the stipes of the fungus. In all my speci- 

 mens, also, the stipes proceeds from the first joint of the body, 

 just behind the head, and projects forward in line with the body 

 of the caterpillar. Some specimens, however, have been met with 

 in which a stipes has sprung from each end of the caterpillar, and 

 others where the stipes has arisen from various parts of the body ; 

 but these are of uncommon occurrence. My own opinion is that, 

 while infection with the spores of the fungus may take place in 

 any of the three ways indicated, the first two are much the more 

 probable. Were the caterpillar to remain unaffected until it went 

 to bury itself, it is scarcely likely that the fungus would grow as 

 rapidly as to stop all attempts to assume the chrysalis form. 



* " Trans. N.Z. InsL," xviii., 209. 



