1898.] 



There are slight variations in other species, but hardly such as can be put 

 definitely into words. 



39, Linden Grove, Nunhead : 

 December, 1897. 



COSSUS LIGNIPERDA: CHANaE OP HABIT OP LAUVA WHEN 

 ICHNEUMONED. 



BY T. A. CHAPMAN, M.D., P.E.S. 



Any change o£ habit of a larva made not in its own interest, but 

 in that o£ a parasite with which it is infested, is worthy of note. I 

 do not itnow whether this instance in the case of Cossus has been 

 noted before or not. 



According to my observations of Cossus, it leaves its burrows 

 when full-fed, makes a hibernating cocoon, and in spring either in 

 this or in a fresh place makes a pupating cocoon. It does not, 

 however, make a cocoon at any earlier period, or in its burrows. 



Meniscus sefosus is a large ichneumon, well known as a parasite 

 of Cossus. I met with its cocoons this year under circumstances 

 shewing that it quitted its host when the latter was rather more than 

 half full-size. A size that I have been used to regard as one year 

 short of full fed, and which Buckler figures as in its second year. In 

 a Cosstts-iniested tree at Sterzing (Tyrol), I found several cocoons, 

 evidently made by Cossus larvae at this stage, as their remains testified, 

 and occupied also by a cocoon of the ichneumon, which had emerged 

 from the destroyed larva after it had spun up. The Cossus cocoon 

 was not a very strong structure, still strong and definite enough, and 

 was made under bark loosened by the Cossus, and in fact in the Cossus 

 burrows, though superficially. The presence of the parasite had, 

 therefore, induced the Cossus to make a cocoon in its burrow, though 

 superficially, again evidently in the interest of the parasite, and to do 

 so when only half fed. 



The variation from natural habit may perhaps be regarded aa 

 due to a premature and weak matui'ity. The larva acts as if full- 

 grown, desires to spin up, and even attempts to leave the burrow, but 

 only succeeds in reaching a superficial portion of it. 



I owe the verification of the name of the ichneumon to Mr. 

 Bignell. 



Ecdlull : December, 1897- 



