1906.] 



219 



the cottage, but these all proved to be ^^ (^ or ? ? of ccdlosus. I pre- 

 sume, therefore, that the active life of this year's colony is now ended, 

 having lasted perhaps from the last week of June to the end of July. 

 1^'rom Switzerland (Geneva) I have males of the species taken as early 

 as May 30th, but in this country it would probably seldom be worth 

 while to look for it till at least a fortnight later. 



M. Fertou in his interesting Observations sur V instinct de quel- 

 ques Rymenopteres (Bordeaux, 189G), points out that the real use of the 

 tubes or " chimneys " constructed by renifonnis and certain other 

 Odyneri is still unknown. A somewhat similar but much larger and 

 stronger vertical chimney is formed by a bee {Eucera obesa) which 

 builds in ihe midst of a thick vegetation, and he suggests that without 

 some such land-mark, especially in windy weather, the bee might have 

 dilliculiy in finding the way back to its hole. But this cannot explain 

 the practice in the case of Odynerus, which builds in open spaces 

 whether horizontal or vertical. Another wasp-genus (Geramius) I have 

 seen in Spain, building tubes like those of Odynerus, but straight 

 (not curved) on bare patches of level soil. It has been suggested 

 that they are meant to hide the holes from parasites running on the 

 wall ; but in the case of O. spinipes they certainly do not succeed in 

 baffling its chief enemies, the Chrysids viridula and neglect a. Another 

 idea is that, when the nest has to be closed, the tubes supply con- 

 venient material close at hand for the purpose ; but for this purpose 

 they seem very needlessly large and elaborate, and, in fact, the tubes 

 often remain practically perfect after the nest is closed. It has also 

 been suggested that they may be protections against rain, wind, &c., 

 but they are themselves so frail and delicate (crumbling at the slightest 

 touch) that any weather likely to damage the nest would, I believe, no 

 less destroy the tube also. And one would also expect, in that case 

 that the form of the tube would differ according as the burrow was 

 formed in a perpendicular oblique or horizontal surface, which does 

 not seem to be the fact. Personally, though doubtfully, I lean to the 

 idea that, at least in some times and places, they may have helped the 

 Odyneri or their ancestors by baffling unwelcome visitors. Though 

 they may fail against Chrysids^ it does uot follow that they are useless 

 against all intruders who might do mischief in the burrows— omnivo- 

 rous beetles, earwigs, ants, mites, Mutillidcs perhaps in some districts 

 etc. Besides, even against Chrysids they may at least oppose delays, 

 though not an insuperable obstacle. Lastly — inasmuch as hereditary 

 instincts may depend as much, if not more, on past as on present 

 circumstances— there is the possibility that Odynerus has simply in- 



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