THE ACULEATE HYMENOPTERA. 103 



whereby all chance of mistake may be obviated ; it is of 

 course advisable in some cases to dig out the females when 

 the males are seen hovering about the fresh turned hillocks. 

 It is only by carefully observing colonies of the different 

 species, that a knowledge of their parasites can be obtained. 

 Great numbers of Andrenidce will be found on Sallow cat- 

 kins, particularly males, but by these means nothing is learnt ; 

 a multitude of specimens will be accumulated, but no know- 

 ledge of the species acquired: by practising the method 

 above recommended of searching for the colonies of bees, 

 and there securing the sexes, immense advantage will be ob- 

 tained and the labour of naming the species reduced by at 

 least one-half. 



Of one or two genera of the Andrenidce, the young col- 

 lector may spare himself the trouble of looking for more 

 than one sex in the spring ; these are Sphecodes and Ha- 

 lictus; of these, the females only will be found until the end 

 of summer and during the autumn, when the males will be 

 found in plenty, and will continue to be so even after the 

 other sex has passed away ; for the history of these bees I 

 must refer the student to my book on the Bees of Great 

 Britain. I would recommend, as regards the wood-boring 

 bees, to notice situations where they are plentiful, forming 

 their nests in posts, rails, &;c. ; the following spring it is ad- 

 visable to procure portions of such wood as they have bur- 

 rowed into — this secures the certainty of obtaining the sexes 

 of the species, and of such parasites as they may be infested 

 by. The same plans which I recommend for adoption in 

 collecting bees, will also apply to the Fossorial tribe, but in 

 some respects the time for capturing the rarer species is dif- 

 ferent; bees should be looked for betimes in the morning, 

 between the hours of eight and twelve, and this, when the 

 weather is moist and calm ; a west, or south-west wind, is most 

 desirable. Some of the fossorial genera, Metlioca, J fust ilia, 



