Mabch 6, 1914] 



SCIENCE 



361 



beginnings of such adaptive modification, and 

 suggests plainly that the beetle's habits are 

 probably already those of a habitual external 

 parasite of its shrew and field mouse hosts, 

 feeding (with simple biting mouthparts) on 

 the dermal scales and hair. 



Professor Van Dyke, of the University of 

 California, our foremost Pacific coast student 

 of the beetles, and from whom I have most of 

 the information used in this note, writes that 

 from the fact of finding LepUnus in the nests 

 of bumble bees a number of entomologists 

 have advanced the idea that the beetle lives 

 normally in bumble bee nests and becomes 

 accidentally carried from them by mammals 

 that raid the nests. " This I do not agree 

 ■with," says Dr. Van Dyke. Considering all 

 of the circumstances of the few captures that 

 have so far been made of the beetles. Dr. Van 

 Dyke concludes that the beetle is a real para- 

 site of the mice and shrews and " absolutely 

 dependent on them in the same way that the 

 Mallophaga are dependent on their hosts." 



Another little beetle, LepUnillus validus, 

 closely related to Lepiinus, occurs on beavers 

 in the Hudson Bay region. Still another 

 beetle, Lyrosoma opaca, a Silphid (carrion 

 beetle), is found in the North Pacific upon 

 practically all of the islands and isolated 

 ocean rocks to be found there. It breeds in 

 rotten kelp and among old and broken murres' 

 eggs, etc., and has been found prowling about 

 the tenanted nests of the murres. But it is 

 wingless, and Dr. Van Dyke believes that it 

 is carried from island to island and rock to 

 rock by the roosting and breeding birds of 

 these rocks and islands, the beetles acci- 

 dentally seeking shelter among the feathers 

 of brooding or perching birds, and thus being 

 carried off by them when they take to flight. 

 " Only in this way," writes Professor Van 

 Dyke, " can I account for the presence of the 

 beetles on Bogoslov Island [the famous re- 

 cent volcanic island of Alaska], for this island 

 is but little over one hundred years old, and 

 the insects are so delicate that they could not 

 possibly survive longer than a few minutes in 

 the Arctic waters." 



These stages in the change from a scav- 



enger's life to that of an external parasite, 

 shown by the series of beetles referred to in 

 this note, are exactly parallel with the transi- 

 tion stages from the wingless Atropids (Pro- 

 cidae) feeding on dry bits of dead organic 

 matter, even to the feathers and organic 

 detritus in birds' nests, to the Mallophaga, 

 feeding on the same bits of feathers and 

 dermal scales, but finding them on the bodies 

 of the birds themselves, to whom they have 

 come to bear the relation of permanent ex- 

 ternal parasites, with no longer any capacity 

 to live off their hosts. The next step for some 

 of the beetles to take would be to become like 

 the Anoplura, and find a more acceptable food 

 in the blood of the hosts. For this their 

 mouthparts would have to be considerably 

 modified, but that would be no difficult matter. 

 Vern-qn L. Kellogg 

 Stanford Univeesitt, Calif. 



SPECIAL ABTICLES 



THE DECOMPOSITION OF SOIL CARBONATES 



It has been found at the agricultural experi- 

 ment station of the University of Tennessee, 

 that excessive amounts of magnesium carbon- 

 ate were entirely decomposed when left in 

 contact with fallow soils in pots protected 

 from leaching. Three types of soil were used, 

 and the amounts of chemically pure precipi- 

 tated carbonate of magnesia, equivalent to 

 16,000 pounds per acre of calcium carbonate 

 were applied, in excess of the lime require- 

 ment, as indicated by the Veitch method. 

 One year after the application the soils were 

 analyzed and found to be strongly alkaline, 

 but practically free of carbonates. Repeti- 

 tion of the experiment in metal rims, using 

 32,000 pounds of magnesium carbonate per 

 acre, under field conditions, afforded the samie 

 observation in every one of eight treatments, 

 four with magnesium carbonate alone and 

 four with carbonate supplemented by manure, 

 the analyses being made in this series after 

 an eight weeks' period of contact. This work 

 was begun in the spring of 1912 and final 

 analyses were made in August, 1913. 



It has hitherto been held that the conver- 



