118 THE ENTOMOLOGIST’S RECORD. 
we know that the American genus Xenodusa, which in that country 
takes the place of our Lomechusa and Atemeles, belongs to the true ant 
guests, and the species are fed and licked by their hosts. ‘These facts 
are likewise just as certain in the case of the just described Xenodusa 
sharpi, Wasm., from Mexico, and the newly discovered X. caseyt, 
Wasm., from Colorado, as if their intercourse with ants had been 
closely observed for ten years. 
Lomechon alfaroi, which I described a little time ago, lives in 
Costa Rica with a big ant, Pachecondyla aenescens, Myra, of the sub- 
family Poneridae, which has a very powerful sting. The discoverer of 
this guest, Herr Anastasio Alfaro wrote on the locality label ‘‘ muerde 
muy fiero”’ (it stings fiercely). It proved a real enigma to find a 
systematic position for this interesting beetle. It did not appear to 
belong to a quite new genus, yet none of the known families seemed 
to own it. At first I thought it belonged to the Hndomychidae as the 
shape of its body was somewhat like a Lycoperdina. This similarity, 
however, was only a deception caused by the beetle’s adaptive characters. 
Its specific characters were hidden under them, as under a mask. 
It necessitated an arithmetical operation to subtract the adaptive 
characters from the appearance of the Lomechon to find the family 
characters. I at last classed it in the Silphidae with a certain amount 
of assurance, of which family it possessed the abdomen, underside and 
legs, all the other characters were purely deceptive. Its apparent 
similarity with the Hndomychidae arose from the shape of the thorax 
in connection with that of the abdomen. The thorax, however, 
resembled more that of a very eccentric Lomechusa or Xenodusa, on 
account of its broad shell-like shape and upward bent posterior angles. 
The head was like that of a Lomechusa, and antenne those of a 
Xenodusa. The peculiar shape of the thorax, head and antenne were, 
however, only adaptive characters, of biological, but not of systematic, 
importance. This new creature from Costa Rica must be, lke 
Lomechusa, a true guest. It possesses big tufts of reddish-yellow hair, 
which, however, are not placed, as in the Staphylinidae, on the sides of 
the abdomen, as that part is completely covered by the elytra in 
the Silphidae, but inside the upward bent posterior angles of the 
thorax. On account of the bunches of tufts of hair which possess 
so much biological importance, as well as its resemblance to a 
Lomechusa, this new ant guest has received the generic name of 
Lomechon. 
Another example of the biological value of adaptive characters was 
given me lately by a Brazilian Staphylinid. This example is all the 
more instructive, as it was not even marked ‘“‘ Found with ants.” In 
spite of this, it was easy to determine a priori, the name of its host. 
Father Badariotti, Congr. Sales., sent one from Lorena (Staat St. 
Paulo) a short time ago, in the same tube with some non-myrmeco- 
philous beetles—a big broad species belonging to the subfamily Quediini, 
which possessed, as far as size and shape, some resemblance to our 
hornet’s guest, Velleius dilatatus. Its peculiar colour and hair-growths 
struck me as suspicious as soon as I took it out of the tube and pinned 
it. The brown red colour and the shaggy hair reminded me at once of 
the big neo-tropical leaf-cutting ants of the Atta family (Oecodoma). I 
took the lens and studied it closely. The femur and tibia were flat 
and shaped like leaves, and the antenne short and pressed to the sides. 
