246 



SCIENCE. 



[N. S. Vol. IX. No. SIR. 



and there a species has had a commercial 

 value, like the lac and dye insects. 



In the Heteroptera there are 11 fami- 

 lies which are strictly plant feeders ; 8 are 

 strictly predaceous ; 3 are both injurious 

 and predaceous ; while the economic value 

 of 13 is more or less doubtful. Most of 

 these last are aquatic and have some value 

 as fish food. 



The insects of the single family of the 

 order Physaptera are injurious. 



In the Orthoptera we have one family of 

 strictlj' predaceous habits ; one which has 

 a mixed food and is partly injurious and 

 partly beneficial as its species become scav- 

 engers ; the habits of 1 family are unknown; 

 while iu the 4 remaining families the species 

 are all injurious as destroyers of vegetation. 



The insects of the single family of the 

 order Euplexoptera are probably beneficial 

 as predatory forms and scavengers. 



The single family of the order Malloph- 

 aga is injurious, containing parasites of 

 birds and mammals. 



In the Corrodentia the habits of the in- 

 sects of the single family are on the whole 

 of little economic importance, though the 

 species are to be classified in the main as 

 scavengers. 



In the Isoptera the forms belonging to 

 the two families are injurious. 



In the Order Plecoptera the species of 

 the single family are practically neutral in 

 their economic relations, although they 

 possess some value as fish food. 



All of the insects of the single family of 

 the order Odonata maybe called beneficial ; 

 the adults are pi-edaceous upon other in- 

 sects and are thus strictly beneficial, but the 

 larvae may in a sense be termed injurious, 

 since they are aquatic and prey upon other 

 aquatic insects which themselves may be 

 food for fishes. 



The insects of the single family of the order 

 Ephemerida are of little economic value, 

 except that they are important fish food. 



Lastly, the insects of eight of the fa-mi- 

 lies of Thysanura are beneficial as scaven- 

 gers and soil markers, while some of the 

 species of one family are somewhat harmful 

 from the damage which they do in house- 

 holds. 



Tabulating the facts thus gained we have 

 the following : 



Injurious as feeding upon cultivated and 

 useful plants, the insects of 112 families. 



Injurious as parasitic upon warm-blooded 

 animals, the insects of 1 family. 



Beneficial as preying upon other insects, 

 the insects of 79 families. 



Beneficial as scavengers, the insects of 32 

 families. 



Beneficial as pollenizers only, the insects 

 of 2 families. 



Beneficial as forming food for food fishes, 

 the insects of 3 families. 



Of undetermined economic importance, 

 the insects of 49 families. 



Families containing both injurious and 

 beneficial forms, 22. 



The totals are : 



Beneficial, the insects of 113 families. 



Injurious, the insects of 116 families. 



Both, or undetermined, the insects of 71 

 families. 



CONCLUSION. 



And now the question is : Are we any 

 nearer the answer of the query in the title 

 of this paper than we were at the start? 

 We have, perhaps, gained by this summary 

 a clearer idea of the economic importance 

 of the class Insecta, and possibly it may 

 appear by this contrasting method that the 

 benefits derived from insects entirely offset 

 their injuries ; but we cannot, in our present 

 stage of enlightenment (and I say it with all 

 reverence), complacently and piously adopt, 

 with the good old rector of Barham, the 

 view that insects, with all the lower ani- 

 mals, were created for man's benefit, God 

 permitting occasional injuries, to use Kirby's 



