XXXVU1 INTRODUCTORY REMARKS. 



the Laparocerus subopacus and Lichenophagus buccatrix, discovered 

 by the Messrs. Crotch in Gomera) may perhaps be strictly attendant 

 on the Semperviva ; though it is impossible to assert this, until fur- 

 ther material shall have decided the question. 



A very small assemblage of species still remains to be noticed, of to- 

 tally different habits, which are peculiar to the shrubs of the common 

 Tamarisk (the Tamarix gallica of European latitudes) ; and it is far 

 from unlikely that the few yet detected (only four in number) may all 

 of them occur in Mediterranean countries. They are Nanopliyes 

 lunulatus, Coniatus tamarisci, Stylosomus biplagiatus, and Coccinella 

 Doublieri, the first two of which I captured in Grand Canary, and 

 the last two in Fuerteventura. Although it is not probable that 

 many other species will be met with of a similar mode of life, I 

 think it almost certain that these will be found, when searched for 

 in the right situations, to be more widely spread over the archipelago ; 

 but, whether truly native or originally introduced, it is chiefly in 

 spots near the coast, of low or but slightly elevated districts, that the 

 Tamarisk may be said to flourish. 



General Considerations. In reviewing some of the preceding re- 

 marks, it will not be deemed out of place if I offer a few observations 

 on one or two points which appear to present themselves for notice, 

 We have seen that there are certain districts and altitudes charac- 

 terized by the presence of Coleopterous forms which are dependent 

 on the kind of vegetation which attains its maximum there and has 

 become dominant. Yet it remains for us to ask whether there is 

 reason for suspecting that any of the latter are but mere states of 

 well-known species which have acquired their present peculiarities 

 through long attachment to the particular plants in connexion with 

 which they are now found. I am fully aware that an inquiry of 

 this nature must open up questions of great difficulty, and concerning 

 which there would be much variety of opinion. In the consideration, 

 however, of all such problems (which are perhaps unsolvable) we 

 can but use the evidence that we possess ; and surely, if the latter 

 is admitted to be necessary at all in attempting their solution, it can 

 scarcely be more available than when gathered into a focus on small 

 insular areas which have been so long and carefully explored. That 

 there are positive limits (even though, by the nature of the case, un- 

 definable) between which all species are free to become modified has 

 generally been received as an axiom ; nor has this primary truth been 

 so much as touched by the ascertained fact that the permitted range 



