COSMOPOLITAN COCKROACHES. 217 



cipally night work that has suffered, as this work was done by- 

 burning the midnight oil, the Rhopalocera would not be greatly 

 neglected. 



As the Colley Hill (perhaps better known as Reigate Hill) scheme 

 has been warmly supported by entomologists, I may be pardoned for 

 introducing the subject. I am pleased to be in a position to state that 

 this favourite hunting ground of London entomologists has been 

 secured by the National Trust for Places of Historic Interest or 

 Natural Beauty, but unfortunately there still remains a debt of £700. 

 Another feature of 1912 is that the same body have taken control, 

 under the bequest of the late Mr. G. H. Verrall, of 239 acres of 

 Wicken Fen. Owing to the heavy succession duties payable on the 

 bequest the Trust felt some difficulty about assuming the guardianship 

 of the property. However, through the generosity of an anonymous 

 donor (whom one suspects to be an entomologist) they have been able 

 to accept the gift, by means of which they will have the control of the 

 greater part of this happy hunting ground (about 250 acres), and as 

 it is their ambition to keep all property under their control in its 

 natural condition, one cannot but think that the National Trust 

 should have the good wishes, or more substantial support of all field 

 workers. Long may Colley Hill, Wicken Fen, and the other 

 properties of the National Trust continue to give pleasure and increase 

 of knowledge to the fraternity of the green net. 



Cosmopolitan Cockroaches. 



By the late K. 8HELF0RD, M.A., F.Z.S., F.E.S. 

 It is not always an easy matter to determine the centre of origin of 

 any given species Avhich has spread over the greater part of the globe. 

 If a species is found all over the world in a more or less domesticated 

 state, but exists in a feral condition in a limited area the matter is 

 simple enough. But the cosmopolitan cockroaches are such very 

 domesticated insects, that throughout the entire area of their 

 distribution they are found, for the most part, only in association with 

 man and his works, houses, ships, factories, plantations, etc. If it 

 should happen that any of these domesticated species exist outside the 

 radius of man's influence in a truly feral condition in neigbouring 

 jungle or forest, it is rather an open question whether or no the species 

 is truly indigenous to that area. On the other hand, if the non- 

 domesticated congeners of a domesticated species occur in a given area, 

 let us say, the Ethiopian region, it is quite reasonable to suppose that 

 the domesticated species originated in the same region as its feral 

 congeners. An overwhelming abundance of a species in any given 

 area is often strong presumptive evidence that the species is not 

 indigenous to that area. This, at first sight may appear paradoxical, 

 but a moment's reflection supplies the explanation ; the natural 

 enemies of the abundant species were not imported with it. The 

 occurrence of the rabbit in Australia and of ]'asser inontaiiiis in 

 Singapore are two cases in point, out of several others. With these 

 preliminary remarks let us pass on to a discussion of our cosmopolitan 

 cockroaches. 



The truly cosmopolitan species are : — 



Blattella yermanica, L. (Sub-fam. Pseudomopinae.) 



