212 ZOOLOGICAL GEOGRAPHY. [part iit. 



immigration across the ocean, in various ways and during a long 

 period. These deficiencies are, on the other hand, quite incon- 

 sistent with the theory (still held by some entomologists) that 

 a land communication is absolutely necessary to account for 

 the origin of the Madeiran fauna. 



First, then, we can understand how the tiger-beetles (Cicinde- 

 lidoe) are absent ; since they are insects which have a short weak 

 flight, but yet to whom flight is necessary. If a few had been 

 blown over to Madeira, they would soon have become exter- 

 minated. The same thing applies to the Melolonthidse, Ceto- 

 niidcTi, Eumolpida?, and Galerucidte, — all flower and foliage- 

 haunting insects, yet bulky and of comparatively feeble powers 

 of flight. Again, all the large genera abundant in South Europe, 

 which have been mentioned above as absent from Madeira, are 

 wholly apterous (or M'ithout wings), and thus tlieir absence is a 

 most significant fact ; for it proves that in the case of all insects 

 of moderate size, flight was essential to their reaching the island, 

 which could not have been the case had there been a land con- 

 nection. There are, however, one or two curious exceptions to 

 f])^ absence of tliese wholly apterous European genera in Madeira, 

 and as in each case the reason of their being exceptions can 

 be pointed out, they are eminently exceptions that prove the 

 rule. Two of the apterous species common to Europe and 

 jNladeira are found always in ants' nests ; and as ants, when 

 winged, fly in great swarms and are carried by the wind to 

 great distances, they may have conveyed the minute eggs of 

 these very small beetles. Two European species of Blaps 

 occur in Madeira, but these are house' beetles, and are admitted 

 to have been introduced by man. There are also three species 

 of Mchc, of which two are European and one peculiar. 

 These are large, sluggish, wingless insects, but they have a 

 niost extraordinary and exceptional metamorphosis, the larvfe 

 in the first state being minute active insects parasitic on bees, 

 and thus easily conveyed across the ocean. This case is most 

 suggestive, as it accounts for what would be otherwise a difficult 

 anomaly. Another case, not quite so easily explained, is that 

 of the genus Acallc?., ■\^lli^^h is verv abundant in all the Atlantic 



