The latter was described from Arizona and has not been 

 hitherto reported from California, I think 1 saw one or two more 

 but failed to net them. I looked carefully nearly every day 

 in this particular meadow, and am sure I did not overlook very 

 many of these Sesiids, so the specimens which I took repre- 

 sented the proportion which were flying about. Indeed, I was 

 so intent on getting the specimens, that 1 did not realize the 

 nice opportunity for observation in insect bionomics, which 

 was before me. There were several species of bees flying very 

 commonly in the field which resembled rutilans to a remarkable 

 degree, but I did not see any that closely resembled animosa; 

 this fact would agree with Wallace's third law of mimicry, viz: 

 "that the species which resemble or 'mimic' those dominant 

 groups are comparatively less abundant in individuals, and are 

 often very rare. " I did not pay enough attention to the bees, 

 their comparative abundance, and the extent to which they 

 flew with the Sesiids, but I could generally distinguish rutilans 

 by close scrutiny, although occasionally 1 got a bee by mistake 

 and also because the bees, 1 believe, were much commoner, and 

 flying more or less with the Sesiids or vice versa. To sum up, 

 in this particular field the bees were very common, Sesia ruti- 

 lans were veiy nearly as common, while S. animosa which were 

 conspicuous were exceedingly rare. 



My excuse in making this short note, is to put collectors 

 and observers on their guard, when they happen to find condi- 

 tions, like the above, which are suitable, to subdue their quest 

 for mere specimens and note the biotic relations of these in- 

 sects; the numbers of the mimics and mimicked, the habits, 

 relations, etc. I believe that conditions as I found them are 

 not common, and I only regret that I did not realize the fine 

 opportunity which 1 had for observations. 



In conclusion, I will add a quotation from Wallace's Nat- 

 ural Selection and Tropical Nature, p. 64. which is pertinent in 

 this connection, as follows : 



"It has been so much the practice to look upon these re- 

 semblances as merely curious analogies, playing no part in the 

 economy of nature, that we have scarcely any observations of 

 the habits and appearance when alive of the hundreds of 

 species of these groups in the various parts of the world, or 

 how far they are accompanied by Hymenoptera which they 

 specifically resemble." 



OS 



