39 



than one-half, have been added since my list of 1858. They are 

 not all new sjDecies, some few among them being European species, 

 whose occurrence in North America has been since averred. 



The number of described Syrpliidae from California, whether 

 identified or not, is only eleven. 



Of the ten new species described in the appendix, Xanthogramma, 

 two Bracliyopae and Arctopliila, represent genera hitherto not 

 recorded in North America. 



I am under obligations to Mr. J. H. A^errall, in London, for some 

 notices concerning Mr. Walker's species, and I have credited them 

 to him, whenever they were new to me. In the sequence of the 

 genera I have followed Schiner, not having been able j'et to investi- 

 gate the subject independently. 



The comparison of the European and North American Faunae 

 of Syrpliidae, leads to the following results : 



1. With but few exceptions, all the European genera occur in 

 North America. The exceptions are a number of the smaller 

 genera (with only one or two species), some of which may be dis- 

 covered yet on this side of the Ocean. Such are Callicera, Psarus, 

 Spatigaster, Petecocera, Platynochaetus, Plocota. 



2. Most of the genera, common to both continents, except the 

 very small ones, are much richer in species in Europe than in North 

 America. This disproportion may partly be accounted for by the 

 fact that some of the genera have been very little studied in 

 America. This applies to Pasagus, Pipija, Chrysogaster and espe- 

 cially Chilosia (the latter in Europe numbers eighty-seven species, 

 while only seven are known from North America). But Merodon 

 (thirty-four Europeans against two doubtful Americans) and 

 Eumeous (thirty-four Europeans against a single doubtful Ameri- 

 can), require another explanation. They , belong to ^the South of 

 Europe and hardly reach Sweden; Avhereas the forms common to 

 both continents are generally northern, circumpolar forms. Both 

 modes of explanation fail, however, with regard to Syrphus (seventy 

 Europeans against eleven or twelve Americans) and the allied genera. 

 Melanostoma, Platychirus and Sphaeroplioria (which number in 

 the aggregate about forty-five European species against eight 



