The Anthrax 



long, stiff bristles, pointing backwards, to pre- 

 vent falls or recoils. 



A similar structure exists in the other species 

 of Anthrax with slight variations of detail. I 

 will confine myself to one instance, that of An- 

 thrax simiata, who thrives at the cost of Osmia 

 tricornis. Her nymph differs from that of 

 Anthrax trifasciata, the Anthrax of the 

 Mason-bee, in possessing less powerful arm- 

 our. Its four climbing-belts consist of only 

 fifteen to seventeen double-spiked arches, in- 

 stead of twenty-five ; also, the abdominal seg- 

 ments, from the sixth onwards, are supplied 

 merely with stiff bristles, without a trace of 

 horny spikes. If the evolution of the various 

 Anthrax-flies were better known to us, the 

 number of these arches would, I believe, be of 

 great service to entomology in the differentia- 

 tion of species. I see it remaining constant for 

 any given species, with marked variations be- 

 tween one species and another. But this is not 

 my business: I merely call the attention of the 

 classifiers to this field of study and pass on. 



About the end of May, the colouring of the 

 nymph, hitherto a light red, alters greatly and 

 forecasts the coming transformation. The 

 head, the thorax and the scarf formed by the 

 wings become a handsome, shiny black. A 



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