184 KANSAS UNIVERSITY SCIENCE BULLETIN. 



species to enable the listener to distinguish between them. 

 Thus Tachytes mandibiilan'a has a higher-keyed hum than the 

 larger T. distinctits. The hum of these wasps is therefore of 

 great assistance to the observer who is desirous of seeing them 

 hunting their orthopterous prey ; for whereas the wasp is often 

 lost to view while flying among the weeds, her audible buzz 

 enables one to follow her with some degree of certainty. 



Some, notably Tachytes, commonly fly quite far from their 

 burrows in search of their prey, while many of the Tachysphe.r, 

 having shorter wings but longer legs than the species of the 

 foregoing genus, are largely cursorial, and seek their victims 

 at no great distance from their tunnels, and, since these wasps 

 seldom move far in a straight line, their course will often 

 bring them again before their nests. 



Prey. 



The prey of the Larridse consists very largely of orthop- 

 terous and hemipterous insects. These wasps are therefore of 

 some economic importance. Where the insect attacked is an 

 orthopteron, it may frequently be far larger than its aggressor 

 (fig. 112), and is then able to offer it stout resistance before 

 being subdued, and not infrequently escapes altogether. In 

 other cases the fated victim is no match for the wa«p, which, 

 clasping it with its legs, readily administers the fatal sting 

 under the thorax. 



As a consequence of an older and more peopled country, the 

 Larridse, in common with many other groups of insects, have 

 been better studied in Europe than in America. In the former 

 country, Fabre observed Tachytes obsolctus provisioning its 

 nest with the larva of Oildipoda. T. tarsina captures a larval 

 acridian, while T. pompiliformis seems to furnish her progeny 

 with a more diversified menu, having been seen by diff'erent 

 entomoloGists to capture lepidopterous larvae, as well as 

 Crthoptera of the fam.ilies Acridiidfe and Gryllidje. Sharp 

 (Carnb. Nat. Hist. Ins., pt. 2, p. 117; 1901) speaks of "a 

 species of Tachytes in the south of France," which selects as 

 its prey one of the ferocious Mantidse, stinging this capable 

 insect, at an available opportunity, in the "nerve center be- 

 tween the formidable arms; . . . subsequently the rac/(y- 

 tes paralyzes each of the other pair of legs, and then carries 

 off its victim." Larra anathema, a large and powerful species 

 of the Old World, provisions its nest with mole-crickets. The 



