1919.1 gg 



later authors had apparently in all cases restored them to it as mere 

 aberrations or, at most, subspecies (= local forms). As a matter of 

 fact, both Dr. Perkins and mj^self have since found that such of the 

 differences in this case as depend on colour (greater or less extension 

 of yellowish markings), though nearly constant, are not so absolutely. 

 One external character, however, seems to be definite, and practically 

 invariable — a difference, namely, in the sculpture (puncturation, etc.) of 

 the head and the mesonotum. And I now find, after dissecting and 

 examining carefully the 5 ovipositors in many specimens of both 

 forms, that the two can be separated quite easily by the very different 

 structural details in their saws. I have as yet met with no case in 

 which this character has failed me, and am satisfied that the difference 

 is sufficient to justify a separation of the two forms as distinct species, 

 one of which — but, of course, not both — must retain the name pi'oposed 

 by Forster, who, so long ago as in 1771, described arcuatus from 

 English specimens. 



In one of these forms, both sexes have the parts of the head (viewed 

 from above) which lie between the " vei'tical area " and the compound 

 eje% remotely, and rather feebly and irregularly, punctui'ed, with polished 

 shining intervals between the punctures. The punctures of the meso- 

 notum are pretty close and regular, but not so close as to make its 

 surface appear opaque. The scutellum is, I believe, invariably marked 

 with yellow, and, as a rule, entirely of that colour. The antennae 

 generally have a yellow mark on the basal joint, but this character 

 sometimes fails. The $ $ have a sharply-defined yellow fascia covering 

 the greater part of the apical margin of the propodeum, but always (I 

 believe) distinctly abbreviated on each side, and so not becoming con- 

 fluent with the yellow matkings of the ventral surface. (N.B. These 

 markings in fresh specimens are more or less greenish, but after death 

 soon turn completely yellow.) 



In the other form, the spaces between the vertical area and the eyes 

 are almost opaque, coarsely and closely punctured ; the punctures of the 

 mesonotum are also rather large (coarse and close) and its sm-face com- 

 paratively dull. The scutellum is almost invariably black, but Dr. Perkins 

 has just sent me a $ — the first with such a coloration ever seen by either 

 of us — in which it is partly yellow ! On the other hand, the yellow 

 fascia on the propodeum seems to be really invariably complete "(i. e. not 

 abbreviated laterally, but running along its whole margin and so uniting 

 at last with the yellow of the ventral surface). This is the case in 

 Dr. Perkins's specimen just mentioned, and it would be difficult to say 

 to which of the two forms it ought to be referred, were it not for the 



