TENT-MAKING CHALCIDS. 85 



Fortunately tliis destructive species is kept mucli in 

 clieck by the attacks of several Ichneumonidai. One of 

 these parasites is a minute but showy little insect 

 belonging to the GlialcuUdre, which differs somewhat in 

 its habits from other Aphidii, in that it undergoes its 

 metamorphosis within a curious silken tent, which the 

 larva constructs after it has become full fed within the 

 body of the Aphis. 



The apterous worm-like grub of this Chalcid per- 

 forates the hard Aphis- shell at the belly, and then 

 commences to spin a double-walled tent between the 

 space comprised by the six legs of the insect. The floor 

 of this tent is attached to the leaf on which the Aphis 

 originally fed, the web being carried up to its skin which 

 thus partially forms the roof. Subsequently the edge 

 of the web is reflected downwards so as to form a 

 chamber with double walls, a considerable space being 

 found between them. 



The spinning process may be conveniently seen by 

 fixing an infected Aphis on a strip of glass. After the 

 grub of the Coryna has fairly commenced to spin, the 

 operation may be viewed from the under side through 

 a low power of the microscope. 



In this cocoon the change into pupa takes place, and 

 after an interval of about nine days the winged 

 Chalcid eats its way out of the silken envelope. On the 

 authority of the late Mr. Walker this insect belongs to 

 the genus Goriina (sic) of Curtis. 



It is interesting to find that there is a controlling 

 economy with reference to this insect very similar to 

 that we have before described in the Ephedrus of the 

 wheat Aphis. Occasionally the silken tent will be 

 found tenanted by several shining black pupse, which 

 have resulted from the metamorphosis of some larval 

 parasites which, between themselves, have consumed 

 the grub of the Coryna before it could attain its 

 imao-o state. 



In some cases it appears that the Coryna (possibly a 

 difi*erent species) does not complete its growth until a 



