CHAPTER III 
GALLS CAUSED BY BEETLES (COLEOPTERA) 
I T 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 
no 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 Cevambycidae (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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