GENERAL 31 



There is no existing list of the known parasites of leaf- 

 miners, but one of us (Frost, '24: 131-132) has compiled a 

 list of those known from Dipterous miners. This list of 67 

 species includes at least one secondary parasite. 



COLLECTING AND REARING LEAF-MINERS 



It is easy to collect leaf-mining larvae. All that is neces- 

 sary is to gather the leaves and hull the insects out from 

 their mines. A fine, curved-pointed pair of forceps is the 

 most useful instrument for this, though a hook-pointed 

 needle in a handle will do it almost as well. The larvae are 

 best preserved in alcohol of about 80 per cent strength. 

 Very soft larvae, like those of the Diptera, are better pre- 

 served if first dropped for a minute in boiling water, before 

 being put in the alcohol. Pupae that are formed in the 

 mines, are obtained and preserved in like manner. But it is 

 very difficult to find pupae in nature when formed outside 

 the mines, and they are better obtained by rearing them. 



The best way to rear leaf-miners when they are common 

 and near at hand is to let them rear themselves as far as 

 possible : to keep watch on their progress and to gather the 

 material when in the desired condition. The one rule for 

 success in rearing any thing is to maintain natural condi- 

 tions. Since this is rather hard to do in parched leaves, it 

 is better to leave them on the stems whenever it is possible 

 to watch them there until the larvae are full fed. Then 

 they may be put in containers provided with proper con- 

 ditions for formation of pupal cells — earth, trash, leaves or 

 rough twigs in the bottom, according to the demands of the 

 species; or if they pupate in the mines, then nothing at all 

 besides the leaves containing them. 



The adult moths, beetles, etc., when they emerge are pinned 

 and mounted by the methods well known to every entomol- 

 ogist. 



Method of collecting Dipterous leaf-mines. For collecting 



