58 ^A^ ECONOMIC ENTOMOLOGY. 



or "commercial" fertilizers. In the manure itself they are bene- 

 ficial rather than otherwise, hastening its decay by changing the 

 form of the more resisting portions. 



It sometimes happens that, when found associated with decay 

 or rot of stored produce, the insects are accused of causing it ; 

 but they always follow and never precede or cause the diseased 

 appearance. 



CHAPTER III. 



THE NEUROPTERA AND PSEUDO-NEUROPTERA. 



May-fiies, Dragon-flies, Stone-flies, Caddice-flies, etc. 



The old term Neiiroptera comprised all insects with four more 

 or less transparent wings, reticulated or netted with numerous 

 longitudinal and transverse veins, and the mouth parts formed 

 for biting. As thus defined the order was easy of recognition, 

 and, practically, the division is convenient here, for nowhere in 

 this series are any species injurious to field crops. We find 

 troublesome species among the parasites, and the Termites, or 

 " white ants," are injurious under some circumstances ; but, as a 

 broad statement, subject to a few exceptions, it is correct to say 

 that no Neuroptcra are injurious to field crops, and no appre- 

 hension need be felt whatever the numbers in which they may 

 appear. 



It was early found that under this term insects quite different 

 in life habits were included, some having complete and some in- 

 complete metamorphoses. The order was then divided, the term 

 Pseudo-neuroptera being applied to those forms in which the 

 transformations are incomplete. The division is a good one ; 

 but, as there is nothing in the adult to indicate to the tyro the 

 nature of the changes it undergoes, it was not always easy to de- 

 cide to which order a given insect belonged. More recently the 

 series has been yet further divided, and we have now somewhat 

 compact groups of net-veined insects which may be recognized 

 without much trouble. ' These will be referred to in order under 

 their modern names. 



