ALASTOR. 375 



venia ntgris. — %. Cljpeo grosse cribrato, superne flavo, apice late 

 emargiiiato. — Variat: Tertio segmento fluvo-marginato. 



AlasLor mexicanus Sauss. Revue de Zoolog., XXII. 1870, 141, 37, J . 



% . Total length, 9 mm. ; wing, 7.5 mm. {var. length, 8 mm. ; wing, 6 mm.) 



Body slender and cylindrical. Head rather thick. Thorax 

 convex, widest anteriorly, rather attenuated behind. Prothorax 

 having its anterior margin crested; its angles rather spiniform. 

 Scutel and post-scutel quite flattened, not at all salient, continuing 

 the surface of the thorax, which is further continued behind the 

 post-scutel by the metathorax. Head and thorax densely and 

 coarsely cribrose. Metathorax narrower, quite rugosely sculp- 

 tured, vertically truncate ; its hinder face quite excavated, 

 polished and sparsely punctured; its margins quite sharp, forming 

 superiorly a semicircle, not interrupted in the middle, trenchant 

 and acutely denticulate; the denticles forming a sort of erect 

 crest; inferior margins transverse, forming on each side a kind 

 of rounded lamella, having a species of tooth at its base, or 

 bilobed. Abdomen quite sessile, shallowly punctured, the first 

 segment not as wide as the second, short, sparsely truncate 

 anteriorly, its anterior and superior face separated by the suture, 

 which makes a transverse ridge, almost a crest, the second seg- 

 ment having its margin smooth, but this is preceded by a line of 

 strong impressed punctures. The following segments having 

 their margins smooth also, the base punctured, and the two zones 

 separated by a transverse impressed punctate line. 



Black. A dot behind the eye, a narrow line on the anterior 

 margin of prothorax, an interrupted margin on the scutel, inferior 

 edges of metathorax, a narrow marginal fascia on segments 1-2 

 of the abdomen, yellow. Feet black ; tibiae witli a yellow line. 

 Wings subhyaline, smoky; nerves black; 2d cubital cell much 

 pctiolate. Wing scales black. 



Var. Smaller. Superior margin of metathorax not denticulate. 

 Third abd. segment marginate with yellow; the 4th with two 

 lateral yellow bordering marks. Wing scales preceded and fol- 

 lowed by a yellow dot. — No yellow dot behind the eye. 



£ . Clypeus rounded, black, coarsely punctured, its; inferior 

 border widely, but not deeply eniarginate. The superior part 

 yellow. Antenn83 black, the scape with a yellow line; the hook, 

 black. 



