88 ANIMAL LIFE 



and when autumn comes the roll-call is complete, for 

 there is no plant more secure from animal interference. 

 The lycopods, the mare's tail, and the vast host which 

 form the vascular cryptogams are passed by and 

 avoided. But when we come to the primitive seed- 

 bearing plants — the pines, the cycads — we find primitive 

 insects, a sawfly, a few wood-borers, squirrels, and a 

 few birds capable of obtaining nourishment from them. 

 It is mainly the flowering plants at the top and the 

 fungi at the bottom of the plant kingdom which 

 constitute the supplies of vegetable food of which 

 animals can avail themselves. And neither by birth 

 nor adaptation have all land animals the taste or 

 the capacity for the requisite work of getting at 

 that nourishment and assimilating it. How an 

 alternative diet — that of flesh — has been maintained or 

 adopted by so many terrestrial animals we may now 

 consider. 



By three paths land animals have become car- 

 nivorous. We have seen that the primitive air-breath- 

 ing animals — e.g., Orchesella (fig. 12) — fed on moulds 

 and lichens, which are found everywhere. From 

 moulds, and especially from fungi, it is but a short 

 step to a flesh diet. In the second place, we saw that 

 piercing and sucking organs were developed as the 

 higher insects discovered the sap or honey of flowering 

 plants, and found that for flight such a diet was emi- 

 nently suitable. For such creatures the transition 

 to parasitism on either plant or animal, or to the habit 

 of sucking the juices of active prey, was an easy one. 



