358 PROTECTION AGAINST INSECTS. 



FAMILY III. CYNIPIDAE (GALL-WASPS).* 

 Description of Family. 



Imagos with straight, filiform antennae, with 13 to 16 joints; 

 ocelli far back on the crown of the head. Forewings with only 

 6 to 8 cells, with no stigma, and with 1 radial and 2 to 3 

 cubital cells. Some species have no wings, or only abortive 

 ones. Abdomen pedunculate, laterally compressed and trun- 

 cate at apex, much shorter than the wings. $ usually very 

 small. Larvae usually thick and fleshy, curved, smooth, white, 

 and apodal. Pupae thick-set, smooth, and white. They are 

 divided into 3 groups : True Gall-wasps, Secondary Gall-wasps, 

 and Parasites. 



1. True Gall- wasps. 



The true gall-wasps bore with their ovipositor into leaves, 

 buds, shoots, fruits and other parts of woody plants, and they 

 insert one or more eggs in the wound. The egg hatches in 

 due time and the larva lives in a chamber formed in a growth 

 or gall, often of hard or woody consistency, formed by the pro- 

 liferation of the surrounding plant-cells. The growth of this 

 gall is not due to the irritation caused by the mother, but to 

 the stimulus caused by the internally-feeding larva. Galls 

 may be on roots, bark, buds, leaves, blossoms or fruits. They 

 may also contain one larval chamber, or many, the former 

 being most usual. The insect usually hibernates in the gall, 

 rarely under dead leaves. 



The oak is attacked by about fifty species of gall-wasp, and 

 galls are chiefly found on badly-growing underwood in coppice 

 or high forest. This is probably due to the fact that tannic 

 acid flows into the gall tissues, which are thus rendered 

 immune to birds. The consequent damage is not serious, as 

 the attack is chiefly on foliage. At the same time galls on 

 buds or bark, when very numerous on seedlings or coppice- 

 shoots, may cause stunted growth. Some species, on account 

 of the tannic or gallic acid they contain, are useful in producing 

 the galls used in commerce. 



Probably the most harmful species is the common marble 



* As the family of Diptera, knowii as Cccitloni i/iiihie, contains ninny species of 

 gall-flies, it is preferable to term the Cynijridac (jull-ivasps. 



