194 Zoology of Colorado 



(4) Psammocharidae, the Spider Wasps. Active, long-legged 



wasps which provision their nests with spiders. In the 

 southwest certain of these wasps are known as Tarantula 

 Hawks; large insects with red wings, which prey on the 

 great hairy spiders. We have many small spider wasps 

 in Colorado, some of them prettily colored. 



(5) Mutillidae, the so-called Velvet-ants, which are not ants 

 at all, but wasps parasitic in the larval state in the nests 

 of other insects, principally bees. They are remarkable 

 for their brilliant colors, and often long hair, and for the 

 great difference between the sexes. The males are winged 

 like other wasps (but the wings do not fold lengthwise); 

 but the females are entirely wingless, and so unlike the 

 males that it is very difficult to match the sexes. A very 

 remarkable member of this group is Myrmilloides grand- 

 iceps Blake, which Mr. Clarence Custer found in some 

 abundance at White Rocks near Boulder, in 1 926. The 

 males are provided with only minute, rudimentary wings, 

 and have the aspect of females. The case appears to be 

 analogous to that of the Seabright Bantam fowl, ex- 

 perimented on by T. H. Morgan. In the Seabright 

 Bantams the male sexual organs carry an inhibitor for 

 the ordinary male plumage of fowls; and they have the 

 external appearance of hens. 



The Sphecoidea are not so varied, and yet include quite 

 diverse elements. The Sphecidae include the Thread-waisted 

 wasps or Mud-daubers, common about houses and in dry places. 

 The base of the abdomen (waist) is slender and thread like, the 

 end more or less enlarged. The mud-daubers make nests of mud, 

 which they provision with spiders. The species of Sphex are 

 usually smaller, and nest in the ground, using caterpillars for 

 provisions. They sting the caterpillars in such a way as to 

 paralyze but not kill them, so that they will remain fresh meat 

 for the wasp larvae. Then when the work is completed, they 

 take a little pebble in their jaws to smooth over and flatten out 

 the soil at the entrance to the hole, so that it cannot be found by 

 possible enemies. These extraordinary facts were fully observed 

 and described years ago by Dr. and Mrs. Geo. W. Peckham of 



