OBSERVATIONS ON WOOD-LICE AND CENTIPEDES 49 



Among forms that make their appearance early are some of the 

 smaller wild bees, and, later on, the life histories of other insects may 

 be followed. The cuckoo-spit insect is common enough, and is a 

 good example of one which does not change very abruptly during its 

 growth. The eggs will no doubt require very careful looking for, 

 but the froth which is exuded by the young and wingless insect is 

 very conspicuous. Specimens should be examined from time to time. 

 At last a day comes when the final change of skin takes place. A 

 frog-hopper now endowed with wings appears, and the froth dries 

 up, revealing its old and empty coat. Many of the gall-flies, to be 

 touched upon in Chapter XXXIII, are |> busy laying their eggs in the 

 spring, and at this time also the insects whose grubs prey upon the 

 larvae of the gall-fly, are actively seeking the latter. 



Turning once more to spiders, we should mention that the water- 

 spider can easily be induced in the early months of the year, to spin 

 its silken " bell " beneath the water and fill it with a silvery globule 

 of air. Any small glass jar will do, though the narrow flat-sided 

 jars used for museum specimens are very convenient, as the spider 

 can be watched more successfully. Of course some fragments of 

 water- weed must be put into the miniature aquarium, to form the 

 foundations of the " bell." 



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