8 PKOCEEDINGS OF THE NATIONAL MUSEUM vol. 70 



to show that the whole group is one species, though with a great 

 amount of variation. 



The amount of yellow present on the legs seems to be very nearly 

 constant. The greater part of the scapes of the antennae and the 

 tegulae are always yellow. The abdomen, except part of the first 

 and very rarely part of the second dorsal segment is always black. 

 The variation, then, occurs chiefly on the thorax, petiole, and first 

 abdominal segment. Beginning with the form having the greatest 

 amount of yellow, we have serviUei, described by Lepeletier in 1845. 

 In this form, the yellow is distributed "as follows : The dorsal part 

 of the prothorax, tegulae, a streak downward below the tegulae, 

 scutellum, metanotum, a spot on each side of the propodeum anterior 

 to the spiracles, a very large spot on the end of the propodeum, this 

 sometimes very much extended forwards, the entire petiole, and al- 

 most all of the first dorsal abdominal segment ; all of this in addition 

 to the constant areas previously mentioned. In some individuals, 

 the petiole, instead of being entirely yellow, has a fuscous streak on 

 the dorsal side ; in others the same area is black ; in still others almost 

 the dorsal half is black. Parallel with this has occurred a reduction 

 in the size of the spots on the propodeum, those at the sides tending 

 to disappear, and that on the end being much smaller. Such speci- 

 mens were described as caefnsntarium by Drury in 1770 and as flavi- 

 punctata by Christ in 1791. Next, the amount of yellow on the ven- 

 tral side of the petiole gradually lessens, until this area becomes en- 

 tirely black. Such individuals were described in 1773 by De Geer 

 as Sp7iex flavoTiKKmlata and by Fabricius in 1775 as Sphex lunata. 



From this point on, the reduction in the alnount of yellow seems 

 to take place in two principal regions — at the end of the propodeum 

 and on the first dorsal abdominal segment. The spot at the end of 

 the propodeum is very much reduced in size in some specimens; in 

 some it is narrowed in the middle; and in still others it is divided, 

 forming two small spots instead of one larger one. This forta was 

 described by Smith in 1856 as canadensis. In other cases the spot or 

 spots at the end of the propodeum have disappeared entirely, giving 

 a form which has not been described. 



Other individuals which retain the spot at the end of the 

 propodeum lose to a greater or less extent the yellow on the first 

 dorsal segment of the abdomen. The lunate mark becomes divided 

 in the middle, and the two spots thus formed "may become reduced 

 to mere dots, or disappear entirely. This variation was described 

 in 1864 by A. Costa as nigriventHs, and in 1845 by Lepeletier as 

 arcJiitectus. 



Parallel with the reduction in the amount of yellow on the 

 propodeum and abdomen has occurred a similar reduction in the 

 amount of yellow on the dorsal surface of the thorax and on the 



