Woodworkers 



Is this a case of alternation of generations in which only 

 one generation has as yet been discovered ? Is it, on the 

 other hand, a rare example of a race of females which, 

 from year's end to year's end, throughout the ages, can 

 reproduce their kind without the aid of males ? It may 

 be so, but it seems unlikely. Perhaps some reader of this 

 page may one day solve the problem who knows ? 



One of the most ingenious galls is the pine-apple gall 

 found on the spruce. The cause of this curious gall is a 

 bug. Towards autumn the larvse which are destined to 

 produce the galls travel to the bases of the spruce shoots, 

 and there they dig their beaks deep in the tissues of the 

 tree. Being bugs, they are all armed with sharp, pointed 

 beaks, and by these means they remain suspended from 

 and attached to a shoot till spring. During the winter no 

 change takes place in the host tree, and the young bugs 

 take no nourishment from it. With the advent of spring, 

 each individual, its beak still buried in the plant tissue, 

 begins to suck the juices of the tree, and then and then 

 only the pine-apple gall begins to be formed. 



Without illustrative figures it is by no means easy to 

 make quite clear the changes which take place during the 

 formation of the gall. At any rate the bases of the leaves 

 begin to swell and, as they are situated close to one another, 

 they gradually fuse to form the gall ; but at the same 

 time some little space is left at their outer sides, so that 

 the result is the formation of a swollen portion of the 

 stem in which there are a number of little cavities, 

 represented by the spaces between the leaves. 



As the aphides grow, for such are these gall insects, they 

 cover themselves with a white, waxy, woolly substance, 

 which affords them some protection. About a month 

 after the beginning of the gall formation the aphides 

 begin to lay their eggs, an operation they continue to 

 perform for about six weeks, and each egg is attached to 

 the spruce twig by a thread-like stalk. The larvae emerge, 

 just about the time the cavities between the leaves of the 



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