OF WASHINGTON, VOLUME XIV, 1912. 201 



of families in Porto Rico are of the family Scoliidae, it would 

 be much better to endeavor to work with these rather than 

 with the species of the family Tiphiidse. 



Under a discussion of geographical distribution Mr. Knab 

 remarked that Diptera as a whole are not as widely distributed 

 as is generally supposed, but when carefully studied are 

 found in most cases to be equally restricted in habitat with 

 other insects not so well equipped for locomotion. Most of 

 the species that show an exceptionally wide distribution are 

 such as are favored by human activities. Aside from these 

 the supposed wide distribution is based largely on inexact 

 identification, similar species in different areas being confused. 

 It will, accordingly, be found that the more obscure species, 

 and the groups least understood, show the widest distribution. 

 Another factor to be guarded against is errors in labeling. 

 These are particularly to be guarded against in the collec- 

 tions of the older entomologists, who cared little for exact 

 data of this kind and often did not affix locality labels to their 

 specimens. Thus the labels on some of the older material 

 in the National Museum collection are obviously wrong and 

 in some cases have gone on record. Some striking cases have 

 turned up among the material from the collection of the late 

 Mr. Coquillett. His collection consisted largely of material 

 collected by himself in northern Illinois and around Los 

 Angeles, California. The collection came to the Museum un- 

 labeled and was afterwards labeled by an assistant. It was 

 inevitable that errors should occur. A striking case is Psoro- 

 phorn cilititu, which was recorded by Dr. Dyar from Los 

 Angeles on the strength of a specimen from the Coquillett 

 collection. The species has not been found in California by 

 anyone else, nor at points farther west than Texas, and Mr. 

 Knab said that he was convinced that the species does not 

 occur in California. Mr. Knab said that he believed that we 

 have another case of this kind in Simnliinu bracteahnn Coquil- 

 lett, the types of which are labeled "Cambridge, Mass." and 

 "Los Angeles Co., Cal." Specimens from other eastern locali- 

 ties have since been turned up, but none from California, and 

 the latter record is to be looked upon with suspicion. 



