LONDON INSECTS 97 



pairs of wings partly thickened. The order is thus 

 a half-way house between the transparent wings of 

 Bees and Dragon-flies, and the thick upper shields 

 of the Beetles and Grasshoppers; and this is the 

 characteristic of many of its members. 



But, as if to break the heart of the beginner, who 

 may have flattered himself that he had at last mastered 

 the first secrets of the entomologist's trade, we find that 

 there are whole families of insects belonging to the 

 order which are wingless. All the known 'ocean 

 insects,' for instance, are classified as Hemiptera. 



There are several of them the naturalists of the 

 Challenger added to the number insects not unlike the 

 Gerris, the little slim long-legged Carnivora which are to 

 be seen racing dryshod over the runs in trout-streams, 

 but they have not a wing of any kind among them ! 



One of the specimens of the order which flourishes 

 much too well in London is the Aphis, the common 

 Green-fly. It is an especial plague of town conser- 

 vatories, probably because our plants, having other 

 difficulties to fight with from which their happier 

 fellows are free in the fresher air of the country, have 

 seldom strength of growth enough to make head 

 against such enemies. The flies seem to come by 

 magic. Two or three appear one day, and a week or 

 two later, if no strong measure is taken, every young 

 shoot is covered thickly. 



The explanation is that the Green-fly is among the 

 most rapid breeders yet known, possibly the most rapid, 

 and, strange to say, is both ' oviparous ' and ' viviparous.' 

 G 



