28 LEAF-MINING INSECTS 



Thereafter it feeds within the narrow space quite as do its 

 leaf -mining relatives; it lies on its flattened back and feeds 

 from the leaflet on the upper side, clearing away the mes- 

 ophyll and leaving only the upper epidermis. (See fig. 41.) 



Conversely, the locust leaf-sewer, Gelechia pseudoacaciella, 

 is said to invade the mines of other little moth larvae when 

 young, later betaking itself to a home of its own between two 

 leaflets sewed together. 



There is a little greenish-yellow midge, Chironomus 

 braseniae, whose larva is a sort of leaf-miner. It trenches 

 the upper surface of the floating leaves of the watershield, 

 Brasenia schreberi, roofing over the trench with loosened 

 epidermis and with frass, and it lives and feeds within the 

 trench as in a mine. Apparently it does this only when 

 well grown; for the trenches are all of about one diameter: 

 they do not increase as do true linear mines with growth. 

 Its earlier larval habits are still unknown. 



Its method differs from true leaf-minmg chiefly in that 

 it cuts the epidermis as it goes. From the middle line of 

 the trench it cuts this in narrow strips extending to the side 

 margin, then it removes the thick palisade cells from beneath 

 them. Then it elevates them at their free inner ends, like 

 the strips of a slat roof, fills in the middle interspace with 

 loose pellets of frass and binds all together with silk. Thus 

 its trench is completely covered. At the end it makes a 

 slight enlargement for a pupation chamber. When the 

 adult midge emerges the empty pupal skin is left partly 

 protruding. Many interesting details are given in Leathers' 

 (1922) account of its work. 



There are in our Southern States little caterpillars of the 

 genus Homaledra, that make covered trenches in the leaves 

 of palmettos and excavate parenchyma from their trenches. 

 There is one species for each surface of the leaf ; H. sabalella 

 chooses the upper surface and lives gregariously in irregular 

 runways that are sheltered under a roof of brownish frass 



