1856.] Entomological Papers. 383 



Paussidas, etc. as well as the latter author's general work on the 

 families, and Lacordaire's on the genera, Coleopterorum, diligently 

 consulted, go as guides a long way, and should, although some of them 

 have by the rapid progress of the science grown rather antiquated, 

 guard against a number of mistakes of a systematic nature. — A.s to 

 whether a beetle be new or not, I admit that in forming an opinion 

 on this question the entomologist situated as above will have quite 

 as much to be guided by a certain tact (not clearly definable but 

 understood by scientific men) as by auything else, and I am 

 forced to concede that under any circumstances almost it is totally 

 impossible to arrive at an indisputable certainty either the one way 

 or the other. This, however, by no means excludes the possibility 

 of his forming an opinion with so much precision as to enable him 

 to pronounce on the matter with a very high degree of confidence 

 and all probability in his favour. In attempting to come to a decision 

 on this difficult point he will receive a first superficial idea from 

 careful reflection on certain accidental circumstances such as 

 size, scarcity, or other peculiarities of the insect in question. This 

 idea, which ever way it may incline, will then either gain or lose in 

 strength by diligent reference to his library, until at length, with a 

 certain amount of tact and judgment, he will arrive at a result, 

 which under such circumstances must carry much weight with it. 

 I shall illustrate this case by an example : If for instance after 

 collecting five years in Ceylon generally and in the Colombo .District 

 more especially, I find at the latter place an insect — say the 

 Chlsenius 5 maculatus described below — for the first time — am I not 

 entitled to consider it as very scarce ? If, on consulting my library, 

 I discover nothing which can possibly refer to it (finding that not a 

 single Chlsenius is marked as occurring in Ceylon), are not the 

 chances greatly in favour of its being an undescribed species ? If 

 again I collect beetles as small and inconspicuous as the Trichop- 

 teryx described below, and consider at the same time that, although 

 they are in certain localities of common occurrence, no professional 

 Coleopterologist has ever collected before me in this Island ; if 

 moreover again my library offers nothing that could possibly refer 

 to them individually (there being hardly an Asiatic species men- 

 tioned), — am I not under these circumstances justified in consider- 



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