FIELD BOOK OF INSECTS. 



larvae are almost wholly unknown in the United States; 

 several species have been worked out in Europe. They 

 are found in moist earth rich in decaying vegetation, upon 

 which they feed; Dr. A. D. Hopkins has found larvae of 

 Medeterus in burrows of Scolytidae and thinks them pre- 

 daceous. ... In adult life all are predaceous, capturing 

 chiefly the minuter soft-bodied flies, which they enclose 

 within their soft labella [lips], after the manner of Sca- 

 tophaga, while extracting the juices." The most common 

 place for adults is on shaded foliage but the sun is by no 

 means avoided. Wet earth at the edge of water is also 

 favored, while Hydrophorus and Hercostomus stand on the 

 surface of water. Thinophilus is partial to sea beaches. 

 Neurigona and Medeterus frequent the bark of trees, and 

 Tachytrechus old logs. 



A question which one always expects, when out walking 

 with non-entomologists, is "What are those little things 

 dancing in the air? " The only way to answer (truthfully) 

 is to catch some and find out, for they may be Homoptera, 

 Coleoptera, Hymenoptera, Diptera, or even some other 

 order. If Diptera, they may belong to any of a number of 

 families; the Chironomids are great dancers (Williston 

 told of such an immense ball that their wings produced a 

 "noise like that of a distant waterfall, and audible for a 

 considerable distance"), but the Empididae are called the 

 Dance Flies. "The males of certain species of Em pis 

 and Hilara have the odd habit of blowing out bubbles of a 

 whitish viscid substance which they carry about with them 

 in the air. It is believed that these toy balloons are 

 attractive to the females" (Kellogg). 



The species vary in size from .03 to more than .5 in. 

 in length. I do not know of any good "catch characters" 

 by which to recognize members of this family. They and 

 the Dolichopodids have the wings noticeably rounded at 

 the tip and the second longitudinal vein ends considerably 

 before the tip of the wing; the eyes of the males often 

 meet; the first and second segments of the three-jointed 

 antennas are sometimes so small that they look like a single 



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