CHAPTER III 

 GALLS CAUSED BY BEETLES (COLEOPTERA) 



IT is estimated there are about 150,000 species of beetles ; 

 of these, about 3,300 have been found in Britain. Very 

 few are gall-causers. Mosley's catalogue gives only eight, 

 Connold, in 1909, observed that the number of gall- pro- 

 ducing British beetles is less than twenty. As a matter of 

 fact, there are more than forty, but the galls caused by 

 the majority are very obscure. Houard enumerates about 

 110 Continental forms. 



Beetles have four wings ; the posterior membranous pair 

 are entirely concealed, when at rest, beneath the hard 

 anterior pair (elytra), which cover the back as a protective 

 shield. The larva is a maggot-like creature with a head, 

 three thoracic segments, and eight to ten abdominal segments. 

 Three pairs of small thoracic legs are sometimes present, 

 but are often wanting ; in some species they are present in 

 the early larval stage, but not in the later. 



The larval condition is occasionally very prolonged. In 

 the Ceramhycidae (Longicorns) the development of the larva 

 frequently extends over a year, but when living under 

 disadvantageous conditions — for instance, in dry wood con- 

 taining little or no nutriment — the larval state may be 

 prolonged to an almost incredible length of time. Imagines 

 have emerged from a table twenty to twenty-eight years 

 after the felling of the tree from which it was made. Sereno 

 Watson relates a case of a certain Longicorn in which it 

 seems probable that the life-cycle extended over a period 

 of no less than forty-five years. 



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