1909.] H. Maxwell-Lefroy : Insects of TirJmt. 315 



seasons of rest are passed in that stage. We have mentioned a 

 few /' cold weather species" but such are far less marked than in 

 other orders and this, which is so marked a feature of our tropical 

 fauna, is here inadequately brought out. 



The Pentatomidae are a family which offer valuable data for 

 faunistic purposes, because they have been more collected than any 

 other families. The occurrence of Cydninae and Graphosomatinse, 

 the absence of Tessaratominae and Urostyhnse, are marked features 

 in comparing a tropical fauna such as this with the nearest sub- 

 tropical one, and this family alone offers good reason for the 

 fundamental , distinctions between sub-tropical and tropical faunae 

 which I have suggested in Indian Insect Life. 



Conclusions. 



(i) The fauna of the Gangetic Plain, West, as a tropical area, 

 consists of a few species, well established and abund- 

 ant, and some less abundant. 

 The well-established very abundant ones may be those 

 that have accustomed themselves to dry heat and 

 having less inter-species competition, and a greater 

 amount of food, become abundant. That is, if a 

 species can live at all, it is likely to do very well if 

 its food is one of the common plants or insects, because 

 there are few plants but manj' of each. That is a 

 characteristic of the tropical zone, whereas in moist 

 sub-tropical areas there is a greater diversity of food 

 plants but less of each; there are in the latter more 

 species, more inter-species competition, a greater 

 diversity of fauna but few reall^^ abundant dominant 

 species. One can see that, if one collects in both areas, 

 very markedly. 



(2) There is a greater fauna of species living in soil than 



there is in a sub-tropical region. Plataspidinae, Gra- 

 phosomatinae, Cydninae are actually largely soil-living, 

 root-feeding forms very largely. They are enormously 

 abundant in this tropical fauna, very scarce in a sub- 

 tropical one. 



(3) A large percentage of the fauna is common also to 



Assam, Burma, Malay Archipelago. 



(4) The fauna owes little to the neighbouring sub-tropical 



ones of the Himalayas. 



(5) It contains a small definite number of cold weather 



species, derived probably from North- West India 

 (the Indus Plain). 



(6) There is no real indigenous fauna ; all is derived from 



areas of older geological formation. 



(7) There is a proportion of well-established species found 



all over the tropical plains ; there is also a proi)ortion 

 probably peculiar to this and the Gangetic Plain, East, 



