Woodworkers 



use. They so mould and work it that it forms a good 

 sized double-chambered shelter, in one compartment of 

 which they live and in the other place their excrement 

 and waste food. But the resin-moth is not a true gall- 

 maker. 



There are real galls in plenty, so let us search for them ; 

 the nearest oak-tree, or, failing that, a willow or rose bush, 

 will probably supply all we need. The oak, however, is the 

 tree for galls ; it bristles with them ; oak apples, spangle, 

 currant, kidney, and artichoke galls are a few picked at 

 random. These galls were familiar objects long before it 

 was known that they were the work of insects, and this is 

 hardly surprising, for the galls are conspicuous, the gall 

 insects minute. 



Before considering any gall in detail, let us try to learn 

 something of general gall formation. We will therefore, 

 in imagination, watch a female gall insect at work ; luck 

 and a convenient oak leaf will supply our need, and luck 

 is an essential. When the insect settles on the leaf we 

 must watch her through a pocket lens, for she is too small 

 to observe with the naked eye. She wanders hither and 

 thither on the leaf, and her movements are by no means 

 easy to follow. 



At length she calls a halt on a small leaf vein, and this 

 is the opportunity we have awaited. From the end of her 

 body a long, fine, thread-like structure is unfolded. It is 

 her ovipositor, and she loses no time in plunging it deeply 

 into the tissue of the leaf. A puncture made, the single 

 egg passes down her ovipositor and is placed in position 

 within the leaf. Following the egg comes a drop of fluid 

 whose purpose was for long misunderstood. The fluid 

 was thought to be the cause of the gall ; as a matter of 

 fact, it is merely used to heal the wound made by the 

 female gall insect. The gall or swelling on the plant 

 may assume the most varied and remarkable shapes, and 

 one fact we must never lose sight of is this, the same 

 species of insect always produces the same kind of gall ; 



73 



