FAM. MEMBRACID/E 



MIMICRY 



The grotesque appearance of many of the species of Membracida suggests at once that the 

 peculiar structures must have been developed as some sort of protective imitation or mimicry. 

 Certainly many of the forms bear a remarkable resemblance to thorns, leaves or other parts of a plant 

 or to other insects. As a result, most observers have apparently assumed that the unusual pronotal 

 developments of these insects are the result of Natural Selection and serve as methods of protection. 

 Poulton (1891 : 1903) has attempted to explain the meaning of a series of forms by mimicry and pro- 

 tective resemblance ; Mann (1912) has noted a protective adaptation in a Brazilian membracid, and 

 various authors have called attention to the resemblance of different species of Membracida: to parts of 

 their hosts. No doubt the appearance of a considerable number of species may be explained by such 

 a theory, particularly in the matter of coloration. The colors of both nymphs and adults of man}- 

 forms tend toward verj' effective concealment. Browns, greens and grays in neutral tones predominate 

 in the color scheme of the family, and these tones blend with those of the leaves and bark of the host 

 plants to an extent which offers excellent protection. 



In the matter of structure, however, a critical study of the pronotal processes from generalized 

 to specialized forms, breeds the suspicion that the subject cannot be lightly dismissed or explained by 

 a mere reference to mimicry. protective coloration, imitation or Natural Selection. A few well chosen 

 examples might seem to illustrate perfectly protective imitation. Such examples would include the 

 genus Umbonia with the peculiar thorn-like dorsal spines, the meinbers of the genus Stegaspis which so 

 remarkably resemble dead leaves, and the species of Cyrtolobus which look like fragments of bark. 

 Another lot would seem also to carry out the same idea but would require a little more use of the imagi- 

 nation in the explanation, as, for example, the species of Bolbonoia and Polyglypta which, with a little 

 stretch of the imagination may suggest seeds, or the unusual forms of Spoiigofihorus which might 

 suggest fungi, or the peculiar multibulbous specimens oi Heteronotus which are said to resemble certain 

 tropical ants. However, when one examines the even more grotesque forms, as represented in such 

 genera as Pyrgonota, Hypsaiichenia, Plerygia, Anchon, and many others, even the wildest flights of fancy 

 fail to suggest a resemblance to nny conceivable part of a plant or other object in the insecfs 

 environment. If one continues this attempt to explain the structures on the basis of protective 

 adaptations he soon reaches the limits of his imagination and is led into the realm of conjecture — 

 which does not provide safe ground for the scientist. 



The truth of the matter is that the great majority of the species of Membracida, in spite of their 

 over-developed pronotums, do not suggest any special type of adaptation for concealment but on the 

 contrary their structures make them rather conspicuous on theii hosts. More often than not, the 

 peculiar processes on the body do not in the least resemble any pai t of their host plant or any known 

 object in their environment. Mereover, the species usually cited as wonderful examples of mimicry 

 or protective resemblance are comparatively rare ; surely not a convincing argument for the Natural 

 Selection theory which is based on utility and on the supposition that those forms which have ihe best 

 imitative structures would increase in number over those lacking such structures. 



We are therefore more incUned to the theory that the evoUition of the pronotum from generaHz- 

 ed to specialized conditions is an example of orthogenesis and that in many cases the exaggerated 

 pronotal developments prove a haadicap rather than an a,dvantage to the insects. 



