16 HYMENOPTERA OF AMERICA. [PART I. 



This circumstance promises to render the study of the species 

 exclusively difficult. 



Division ZETHUS 1 (sensu strictiore). 

 (Sadss. Vespides I, 9, III, 115.) 



Second abdominal segment subsessile ; expansion of the petiole 

 globular, lengthened. Thorax moderately lengthened. Meta- 

 thorax convex, presenting two rounded convexities, separated by 

 a groove. Antennae of the males terminated by a spiral. The 

 6th abdominal segment bearing underneath two lamellar appen- 

 dages (copulative?). Species large, having a feeble sculpture, 

 but not polished and with a dull metallic color. 



It is impossible not to be struck with the resemblance of these 

 insects to the Synoeca. The same form of head, indented be- 

 hind, the same dull metallic color, great size, pediculate abdomen, 

 mandibles almost the same form, etc. 



The representatives of these two genera inhabit also the same 

 countries of America. There is, in their color and appearance, 

 one of those analogies which we sometimes find impressed upon 

 insects of the same regions of our globe, 2 and this seems especi- 

 ally one of those openings that modern zoology should carefully 

 mark as suitable to cast some light on the relationship of species- 



1. Z. coeruleopennis 3 Fabr. 



Vespa coeruleopennis Fabr. Ent. syst. Snppl. 263, 1798. 



Zetlius coeruleopennis Fabr. S. P. 2S2, 1.— La'tr. Gen. IV, 137; Encycl. 



pi. 393, fig. 12, 13.— Sauss. Vespides, I, 9, 1 : Revue Zool. X, 1858, 64. 

 Zethus brasiliensis Sauss. Vespides I, 10, 2, J ; III, 115, $ (prob. variety 



of this species). 

 Zethus magnus Sauss. Vespides I, 11, 4, pi. viii, fig. 5, % . 



Abdominis petiolo globoso-clavato, sulco tenuissirae partito. 

 Hab. South America, Cayenne, Para, Brazil, Quito. 



1 I have separated from this division a certain number of small species, 

 whiah have very much the same form of abdomen, but which, by their 

 clypeus and the angular form of the metathorax, find a more natural 

 place in the division Zethusculus. 



2 The Vespides of Chili present a yet more striking example of this. 

 See below Uypodgnerus. 



3 Tbe Vespa surinama Lixx. (Gmel. V, 2759, 23), is either this species 

 or a Synoeca. 





