1 907- 1908.] Galls^ Gall-makers, and Cuckoo Flies. 41 



Hessian-fly, Cecidomyia destructor, which devastates wheat 

 and barley crops. It is called the Hessian-fly because it was 

 supposed to be introduced into America with the Hessian 

 troops employed in the War of Independence. Other farm 

 and garden pests belonging to this family are the wheat-midge 

 or red maggot, the orange-midge, the pea-midge, the pear- 

 midge, and the turnip-fly. Gall-midges are small, slender- 

 bodied, dark-coloured flies ; the females are provided with an 

 ovipositor of less complicated structure than the corresponding 

 organ in the gall-wasps, and their larvse are generally of a 

 beautiful orange colour. 



The galls of Cecidomyia urticse are very abundant on the 

 common nettle. They grow on difl'erent parts of the plant 

 as irregular swellings, sometimes on the basal lobes of the leaf, 

 often as irregular masses on the inflorescence. When opened, 

 each cavity is seen to contain a single white larva. On the 

 various bedstraws swellings of a red or dull purple colour are 

 produced by C. Galii ; they are especially common on the 

 Lady's-bedstraw, Galium verum. The leaves of the meadow- 

 sweet (Spirsea ulmaria) are frequently studded with hard, 

 pear-shaped green or red galls, each occupied by an orange 

 larva of C. Ulmarise. Another common gall is that on the 

 Germander speedwell (Veronica Chamsedrys) ; it consists of a 

 terminal bud with swollen, overlapping leaves, having the 

 orange larvae of C. veronicfe in their axils. Externally the 

 gall is reddish in colour, and is covered with grey hairs ; 

 within is a padding of hairs. The very similar galls of 

 the C. thymicola occur on the ends of the branches of the 

 wild thyme. The two last mentioned are supposed by some 

 to be really mite-galls which have been appropriated by gall- 

 midges. On the umbels of the wild carrot when the plant 

 is coming into fruit one may find here and there a fruit 

 enlarged to twice its ordinary size. Each loculus of the two- 

 celled ovary is occupied by a single orange-coloured grub of 

 Cecidomyia. Other galled fruits which have been vacated are 

 also to be seen with two little round holes at their base. 

 This species, according to Connold, completes its metamor- 

 phosis inside the gall, but this is not invariably the case : 

 many gall - midges, however, do pupate within it, and only 

 leave the gall as winged insects. The globular and ovate 



