40 Galls, Gall-makers, and Cuckoo Flies. [Sess. 



of the oak, and a number of others, also make their appearance 

 during the autumnal months. Much earlier in the season the 

 clusters of the currant gall may be observed on the twigs and 

 catkins ; in May and June the oak-apple is found, a large 

 polythalamous gall, an inch or more in diameter, of a soft 

 spongy consistency, but with a hard centre containing numer- 

 ous larval chambers. From its supposed soporific properties, 

 it is called in Germany the Schlafapfel, or sleep-apple, a name 

 sometimes also applied to the mossy bedeguar of the rose. 

 The acacia apple is the gall of an Australian cynipid ; the 

 apples of Sodom, referred to by Josephus and other writers 

 of antiquity, are by many competent authorities considered to 

 be the galls on a species of oak produced by Cynips insana — 



" Dead Sea fruits that tempt the eye, 

 But turn to ashes on the lips." 



The so-called flea - seeds are also oak-galls formed by a 

 Californian gall-fly, C. saliens. These galls jump about on 

 the ground in consequence of the active movements of the 

 larva enclosed in the thin-walled cavity of the gall. The 

 Hymenoptera make galls on many other plants besides the 

 oak, among others on species of Hieracium, Hypochseris, 

 Grlechoma, Rubus, Salix, Potentilla, Centaurea, Prunus, Festuca, 

 Vaccinium, &c. 



II. 



Next in importance to the Cynipidse as gall-makers come 

 the Cecidomyidae, a family of Diptera. These gall-gnats, or 

 gall-midges, are distinguished from the gall- wasps or true gall- 

 flies chiefly by having but two wings ; they have also much longer 

 legs, and are nearly related to the daddy-long-legs or crane- 

 fly. Their galls are not generally so elaborate as those of 

 the Hymenoptera, but every gradation occurs from leaves but 

 slightly rolled and thickened at the edges up to completely 

 closed galls, hardly to be distinguished from those of Cynips. 

 Many of the Cecidomyidse live on decaying substances or feed 

 on plants without producing conspicuous distortions, and as 

 a rule these are more hurtful to cultivated crops than the 

 gall-making species ; this applies, for example, to the dreaded 



