250 THEORIES OF MIMICRY 



when disturbed. Similarly with the species of various 

 Orders which resemble Hymenoptera. The case of 

 Coleoptera recently suggested to me by Mr. Gahan is 

 peculiarly interesting. It is known in so many cases that 

 beetles which are about by day possess finely facetted 

 eyes as compared with the larger fewer facets of the 

 nocturnal species, that it is possible to infer the habits 

 from the structure of the eyes. Thus the species of the 

 Longicorn genus Doliops (Family Lamiidai), which closely 

 resemble weevils (see p. 261), are, judged by this standard, 

 diurnal in their habits. The case is all the more inter- 

 esting, inasmuch as such an eye-structure, such habits, 

 and such mimicry are quite exceptional in the Longicorn 

 group, the Niphoninae, to which the genus belongs. 



The facts recorded above imply such a relationship 

 between the nervous systems and sense-organs of the 

 various species as will make them, like their models, 

 diurnal (or in some cases semi-diurnal) in their habits. 

 This constitutes a further grave difficulty in the way of 

 any explanation based on External or Internal Causes. 

 If the diurnal habits are supposed to be due to such 

 causes, the greatly increased complexity of the result is 

 the difficulty. If the resemblances are supposed to be 

 thus produced only in the species which are already 

 diurnal, it is impossible to explain why the external or 

 internal forces are thus restricted in their operation. 



It is hardly necessary to point out that the time and 

 space relationships, which are such a difficulty in the way 

 of the other two theories, are entirely necessary to the 

 explanation based on the theory of Natural Selection. 

 If they did not exist it would be overthrown. 



] 1. The Resemblances which Insects of various Orders 

 bear to those of another Order are produced in the ?uost 

 Diverse Ways. 



The most common types for mimetic resemblance 

 are those of the wasp and ant. These aggressive, 

 abundant, and successful forms are resembled by insects 

 of various Orders. Still more interesting is the fact that 

 the resemblance is produced in the most varied ways. 



