64 The Scottish Naturalist. 



air that has obtained admittance within, into irregular eleva- 

 tions ; which, taken along with their seared tint and irregular 

 outline, might induce one unaware of the mode in which they 

 were produced, to infer that the leaves had been injured by the 

 application of some hot or acrid substance. But this is not the 

 origin of these striking appearances ; for it is, in reality, owing 

 to the operations of a company of maggots of a Dipterous fly, 

 about the size of the smallest of the common house flies, and 

 not very unlike to it in general aspect. The parent fly deposits 

 her ova at short distances from each other on the upper sur- 

 face of the leaves ; and the maggots, when hatched, immediately 

 proceed to scoop out and devour the green substance amidst 

 which they find themselves placed ; where, working forwards 

 in drifts, that gradually enlarge with their growth and capabilities 

 of eating, these at length become connected in one wide area, 

 round whose borders the busy occupants continue to ply their 

 vocation, apparently unaware of each other's proximity, and 

 acting without concert in the common field whose limits are 

 only determined by the outline of the foliage. These excavated 

 spaces vary in dimensions. The indwellers sometimes after 

 raising a small blister desert it for another habitation ; or, after 

 entirely consuming the contents of the upper surface of one 

 leaf, proceed, to attack in a similar manner another conve- 

 niently accessible. Where the attacks have been only partial, 

 but frequently repeated, the leaves are much disfigured, and 

 the blotches appear like foul eruptions breaking forth from every 

 part. In some instances we meet with only a solitary occupant, 

 and this is generally the case with the sorrel (Rumex acctosa J, 

 which is mined by the same sort of maggot. In the long leaf 

 of the curled dock ( Ramex crispus), the central portion is the 

 most liable to be eaten out. When this happens, the thin filmy 

 skin is left nearly unbroken, stretchecT between the oblique sides 

 of the leaf, and looks like a large scald, extending from the 

 base to the tip. When fresh, the detached cuticle is white, 

 particularly in the sorrel, variously defiled with green stains, 

 and the ejecta of the miner, but at length it becomes of a 

 pale brown. Its thinness sometimes enables one to trace the 

 outline of the inmates beneath ; in other instances we can 

 only detect their situation, by passing the finger over the 

 surface. 



