g^g The Philippine Journal of Science 1923 



MIMETIC RELATIONS 



Another very peculiar and outstanding feature of the Pachy- 

 rrhynchides is the remarkable resemblance in color and markings 

 of species found together in the same locality or on the same 

 plants, but belonging to different genera of this group, or to 

 different families of Coleoptera, or to different orders of insects. 

 In most instances the color patterns of the different species occur- 

 ring together and resembling each other are of course not exactly 

 the same, but the general appearance and behavior of the beetles 

 produce the effect of extreme similarity. Table 1 gives a number 

 of such species which were actually observed occurring together. 



I have endeavored to ascertain a reasonable explanation for 

 the value that attaches to the similarity in color patterns of 

 different species of Pachyrrhynchides apparently manifesting 

 certain mimicry relations to each other as demonstrated above. 

 Concerning the question 0$ protective mimicry, we assume that 

 the species serving as model is a more abundant form, qualified 

 and protected by special features and logically older than the 

 other species or counter-likeness — the mimetic or unprotected, 

 more recent, and scarcer form. Referring to the species in the 

 list the outstanding fact is that most of those that exhibit 

 such great resemblance to each other are pachyrrhynchids 

 belonging to different genera of this group. All of them have 

 the same general hardness and in none was I able to detect any 

 special glands or other organs which would serve as a protective 

 device. By actual experience in collecting them I observed that 

 in nearly all cases the species belonging to the genus Pachy- 

 rrhynchus were commoner than were those belonging to the 

 genera Metapocyrtus and Macrocyrtus, the last named being 

 much scarcer. So far, I have been able to obtain but little 

 evidence concerning the natural enemies of these beetles, such as 

 birds, etc., although I am inclined to believe that they do have 

 some rather specific natural enemies. Perhaps their extreme 

 hardness and compactness is in itself the protective feature that 

 prevents most birds from eating them. 



Frogs and toads are to be considered as general enemies of 

 the Pachyrrhynchides, of other Coleoptera, of all other orders of 

 insects, as well as of spiders, centipedes, and even small crus- 

 taceans. In August, during the rainy season of 1923, Mr. Ed- 

 ward H. Taylor collected a number of frogs and toads in and 

 around Baguio, Benguet Province. Through his kindness I was 

 able to examine the stomach contents of twelve large frogs, 



