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GUIDE TO CALIFORNIA INSECTS. 



called transverso-cubital veins. The cubital vein arises from the basal cross- 

 vein. On the other side of the cubital there are usually two cross veins 

 which because of their direction are called recurrent veins. 



A system of formulae has been devised for expressing the salient features 

 of a venation and to aid In rapid identification of groups. The plan is to 

 number the bars surrounding the dlscoldal cell between the recurrent veins. 

 The first recurrent vein is numbered 1, then along the cubital to the first 

 transverso-cubital vein Is numbered 3. etc. Even numbers are given to the 

 bars beneath the cell. Where bars are without the cell as is common with 

 bar 3, it Is indicated by as *. The formula consists in naming in the order 

 of size, the bars of a venation, enclosing in parentheses such as may be 

 about equal in size. 



Below will be found the formula of most of our genera of bees: — 



Colletes 4 1 6 2 3* 7 5 9* 



Prosopls 4 15 6 2 7* 



Andrena 4 15 2 6 3* 7*— 4 1 (2 6 7) 3* (5 9*) 



Hallctus 1 4 6 3* 7 2 9* 5—4 1 7 2 3* 9* o 

 1 4 6 (2 7) 3* 9* 5 



Sphecodes 1 6 4 2 7 9* 3* 5 



Agapostemon 4 1 6 7 2 3* 9* 5 



Calllopsis 4 1 6 5 2 3* 7* 



. Panurginus - 4 1 (5 6) 2 3* 7* 



Diandrena 4 1 6 5 2 3* 7* 



Perdita '15 2 3* 



Anthophora 14 6 2 7 (3* 5) 9*— 4 1 6 2 7 3* 5 9* 



Melissodes 4 1 7 (2 6) 3* 5 9 



Tetralonia 4 1 7 2 6 3* 5 8* 



Xenoglossa 4 1 7 6 2 3* 5 9* 



Pseudomelecta 1 4 6 2 3* 7 9* 5 



Eplolus 1 4 6 2 7 5 3* 9* 



Xylocopa 4 1 6 5 2 7* 3* 



Alcidamia 4 1 6 2 5 3* 7* 



Anthidium 6 5 4 1 2 3* 7* 



Chelostoma 4 1 5 6 2 7* 3* 



Megachile 4 5 1 6 2 3* 7* 



Osmia 4 1 6 5 2 3* 7* 



Ashmeadella 4 1 6 5 2 3* 7* 



Nomadidse Nomada 1 4 6 2 3* 9* 7 5—1 4 6 2 3 7 (5 9) 



Melecta 4 1 6 2 3* 7 9* 5 



Ceratinidse Ceratina 4 1 6 7 3* 2 9* 5 



Bombus 4 1 6 7 5 2 3* 9* 



Bombld£B Psythyrus 4 6 1 7 2 5 3* 9* 



Apidae Apis 4 5 6 1 2 7 3* 9* 



Colletldse 



Prosopidae 



Andrenldffi 



Panurgidas 



Anthophoridffi 



Melectidae 



Xylocopidae 

 Megachilidse 



