28 PROCEEDINGS OF THE ACADEMY OF [1896. 



The coloration of the head and thorax is black, green or blue ; 

 frequently the parts are not colored alike, the metathorax especially- 

 being usually bluer than the mesothorax and scutellum. The 

 metallic color does not extend on to the abdomen, except to a slight 

 extent in intermpta. The sculpture of the metallic portions differs, 

 and a good character is found in the smoothness or otherwise of the 

 mesothorax ; in some it is very smooth and shining, in others gran- 

 ular or striatulate and comparatively dull. The dulness or other- 

 wise of the front, and the puuctation of the area close to the ocelli^ 

 may also be used. 



The pale markings may be absent ; when developed they are 

 from pure white to deep yellow, never red, though the yellow of 

 many males may be reddened by cyanide. The reddest color ob- 

 served is in the bright orange-rufous of the latter end of the abdomen 

 in crotonis, and the orange-rufous legs of foxi. The abdomen, as in 

 latior, may be bright ferruginous. These colors are entirely differ- 

 ent from the scarlet induced by cyanide. In some species which 

 live on yellow flowers {hdeola, heata, larrece) the whole body -color 

 is deep yellow, the dark markings being reduced to a mininmm. 

 No species is known similarly white, nor is any species all rufous 

 like some forms of Noinada. 



The head may be comparatively small, round, or broader than 

 long or longer than broad ; in some species it is very large and sub- 

 quadrate. The males may or may not have a conspicuous tooth or 

 spire on the cheeks beneath ; this character appears to be a valid 

 specific one, but appears in species which are not closely allied, (e. 

 g., larrece and pulchrioj-'), while it distinguishes certain forms from 

 their closest allies, as pulchrior from pallidior, the latter having un- 

 armed cheeks. It is to be observed that in the Mutillid genua 

 Sphcerophthahna a similar state of affairs occurs, only it is the 

 females that possess the armed cheeks. Thus *S. montivaga is ex- 

 tremely like S. megaeantha, but lacks the spine on the cheeks. S^- 

 towneyi also differs from its allies by its spinose head. The charac- 

 ter is, therefore, one of those which has been termed " kaleido- 

 scopic." 



The mandibles may be bifid at the tip (latior, texana), or may be 

 notched within (sphceralcece 9 ) or even present a distinct tooth on 

 the inner side (oRneifrons). They are, however, usually simple, and 

 more slender in the males. In the females of the albipennis group 

 they are very stout and strongly elbowed, quite different from the 



