v i INTRODUCTION. 



It will perhaps be of interest to mention some of the genera which are either peculiar 

 to Mexico or Central America, or have very many representatives there. This is all we 

 can do at present, as we scarcely have as yet any knowledge of the life-history of any of 

 the species. It is probable that the larvae of these insects play some part in checking 

 vegetation, as is the case with many species in the temperate zone, where they often 

 seriously injure crops and cereals. Yet it is difficult to believe that the luxuriant 

 tropical vegetation should be at all seriously affected by the ravages of the Phytophaga, 

 while on the other hand a very considerable number of them probably fall victims to 

 birds or other enemies. Be this as it may, there is no doubt that the Eumolpidse, 

 especially the metallic species, and the still more numerous Galerucidse (Diabrotica, &c.) 

 swarm in Central America, and are a feature amongst the Coleoptera of that region. 



Amongst the Sagridse, Aulacoscelis has 11 species, 2 only of which were known at 

 the date of publication of Gemminger and Harold's Catalogue. Amongst the Eumol- 

 pidse, the genus Euphrytus, characterized in this work for the first time, has 17 species, 

 and Promecosma 19 species, all of which are peculiar to Mexico. It is, however, 

 among the true Chrysomelid&e that we find genera numerously represented by species 

 which are for the greater part peculiar to our region ; these are Calligraphy Zygogramma, 

 Leptinolarsa, and others, for the most part containing neatly marked, closely allied species, 

 distinguished by the peculiar pattern of the elytra and their system of punctuation — 

 characters apparently depending on each other for their development. These genera 

 have their head-quarters in Central America, North and South America each possessing 

 comparatively few representatives. As regards the numerous new genera of Halticinae 

 and Galerucinse described in this work, it is impossible to say anything at present 

 about their geographical distribution, as it is highly probable that some of them 

 extend beyond our limits. 



Owing to the great variability of the Phytophaga, more particularly of the Galeru- 

 cidse, our immense amount of material has increased the difficulty of accurately 

 defining the limits of particular species, instead of diminishing it as might have been 

 expected. If the extreme varieties only of certain of them were available for examina- 

 tion, they would in most cases be considered as specifically distinct, the variation not 

 only affecting colour, but, in some species, shape or sculpture also. So that, until the 

 limits of variation are better understood, nothing can be done by the systematic 

 worker but to treat as distinct such forms which in his opinion differ sufficiently from 

 their allies. 



