296 The N ahiralist in La Plata. 
portion of America. The vizcacha does not benefit 
himself alone by his perhaps unique style of 
burrowing; but this habit has proved advantageous 
to several other species, and has been so favour- 
able to two of our birds that they are among the 
most common species found here, wdiereas without 
these burrows they would have been exceedingly 
rare, since the natural banks in which they breed 
are scarcely found anywhere on the pampas. I 
refer to the Minera (Geositta cunicularia), which 
makes its breeding-holes in the bank-like sides of 
the vizcacha’ s burrow, and to the little swallow 
(Atticora cyanoleuca) which breeds in these ex- 
cavations when forsaken by the Minera. Few old 
vizcacheras are seen without some of these little 
parasitical burrows in them. 
Birds are not the only beings in this way related 
to the vizcachas : the fox and the weasel of the 
pampas live almost altogether in them. Several 
insects also frequent these burrows that are seldom 
found anywhere else. Of these the most interesting 
are : — a large predacious nocturnal bug, shining 
black, with rod wings ; a nocturnal Cicindela, a 
beautiful insect, with dark green striated wing-cases 
and pale red legs ; also several diminutive wing- 
less wasps. Of the last I have counted six species, 
most of them marked with strongly contrasted 
colours, black, red, and white. There are also 
other wasps that prey on the spiders found on the 
vizcachera. All these and others are so numerous 
on the mounds that dozens of them might there be 
collected any summer day ; but if sought for in 
other situations they are exceedingly rare. If the 
