350 BULLETIN UNITED STATES GEOLOGICAL SURVEY. 



• 



Mediterranean and Central Asiatic region, extending from Portugal to 

 Turkestan, and embracing Southern Europe and Northern Africa. It 

 is also characterized by the prevalence of Heteromera among the 

 Coleoptera and of Bombylidce among the Diptera. It displays a remark- 

 able unity of character through that vast expanse of country. The 

 very striking genus Julodis (Buprestidoi) occurs in Spain as well as in 

 Turkestan, and nowhere else, except at the Cape of Good Hope. The 

 small family of Glapkyridw (Lamellicornia) is almost exclusively confined 

 to the same Mediterranean region, and also, although in other forms 

 to the Cape. The genera Cleonus and Braoliycerus (Rhyncophora) living 

 on sandy soil and in hot situations characterize the same Mediterranean 

 and Central Asiatic region. 



The same unity of character distinguishes the North American west- 

 ern fauna. Besides the Melasomata and other Heteromera, which occur 

 in increasing numbers from the Plains of Kansas and Colorado to Cali - 

 fornia, the entomologist is struck by the occurrence of other forms of 

 Coleoptera, unknown in the Atlantic States ; for instance, the Dasytidce, 

 which occur in Colorado and in California, and are also represented in 

 Europe. Masaris, a very peculiar genus of Vespidce, for a long time 

 known only from Algiers, has been found since in the Rocky Mountains, 

 in Texas, and in California. A number of Odonata occur in California, 

 in the Yellowstone region, and in Colorado, but do not extend farther 

 east. Among the Diptera, I will quote some leading s pecies, as Taba- 

 nus punctifer, Silvius gigantulus, Eupeodes volucris, Lordotus gibbus, the 

 genus Ospriocerus, which occur in the whole western region, and not in the 

 Atlantic States ; Lordotus, Eupeodes, and Ospriocerus, being new gen- 

 era, as far as known, peculiar to that region ; Silvius, a European genus, 

 which, if it occurs at all in the Atlantic States, must be exceedingly 

 rare. The very remarkable case of Si/rphus pyrastri, a European Syr- 

 phid, very common in California, and also found in Colorado and New 

 Mexico, but never east of the Mississippi, will be discussed below. 



The resemblance between the western and the Mediterranean and Cen- 

 tral Asiatic fauna, is an analogy, due to the identity of meteoric condi 

 tions; it is not a relationship. The same families of insects will prevail, not 

 necessarily the same genera. Thus, among the Heteromera, the great 

 majority of genera iii both regions are different. The Diptera are more 

 cosmopolitan in the distribution of their genera. Such large genera as 

 Bombylius, Anthrax, Stenopogon, Saropogon, belonging to dry regions, 

 are the same in the Old World and in North America ; but, in the same 

 families, Bombylidce and Asilidoe, a number of small genera occur, pecu- 

 liar to each region. Cases of identity of small and exclusive genera, like 

 the above-quoted one of the Yespid Masaris, are for this reason very in- 

 teresting. Pedinocoris braclionyx Mayr is a large aquatic Hemipteron, of 

 which I brought specimens from San Diego, Cal. Mr. Uhler tells me 

 that the same genus is known to occur in Egypt and Turkey. Among 

 the Diptera, I will name the small genus Xestomyza, a singular Therevid 

 represented in the Mediterranean fauna, at the Cape, and in California. 





