422 NATURAL HISTORY OF ARTHROPODS. 



short probosces or none, taking no nourishment in the adult state. They are gen- 

 erally slow and feeble in their movements. The eggs, which are black in color 

 and numerous, are deposited upon the dried twigs of trees. Lasia Mettii from 

 Arizona is of a metallic green color with golden reflections, and the proboscis is 

 one-half longer than the body. 



The family Empid^ is a large one, but chiefly occurring in cold or temperate 

 regions. About eleven hundred species are known. They resemble the Asilidas very 

 much in their habits as well as in their form, though they generally are small in size 

 The head is spherical, the eyes contiguous above in the males ; the head above is not 

 excavated, the third joint of the antennae is simple, with a terminal style, or a terminal 

 or dorsal bristle. The basal cells are elongate, the third vein sometimes furcate, and 

 there are three or four posterior cells. 



The larvae are cylindrical, with small swellings for locomotion on the under side 

 of the mesothoracic segments. They are probably carnivorous, and live in the earth, 

 under leaves, or in decaying vegetable matter. The pupae are free, with two porrect 

 points at the anterior end. 



Many of the species are observed in the early spring, dancing in large swarms over 

 streams of running water. They are exceedingly voracious in their habits, feeding 

 chiefly upon other flies. Many run about with great swiftness, reminding one. of the 

 following family, which they also in their early forms strongly resemble. As in the 

 Asilidae they make much use of their front legs in capturing and holding their prey ; 

 in consequence we find many structural peculiarities in these members, as also is the 

 case with the Dolichopodidas. Such may consist m thickening of the joints, 

 in elongation, in peculiar discs of hair, or in being bent ; in some they are peculiarly 

 prehensile organs, the coxae being very long, and the femora being thickened and 

 armed with spines beneath. Man}' pursue their prey on foot, and will carry about 

 with them insects even larger than themselves, impaled upon their murderous pro- 

 bosces. As is the case among the Asilidae, the female not only resents the advances 

 of the male, but, should he be so luckless as to place himself within her power, she 

 would despatch him without compunction ; hence it is that the male seizes the oppor- 

 tunity to make his advances when she is too busily engaged feasting upon some insect 

 to be able to devour him. 



The family Dolichopodid^ includes a very large number of small, usually 

 brilliant blue fer green, active and predaceous flies, nearly all of which are beneficial 

 to the agriculturist. They may be distinguished by the first basal cell being short, 

 the second united with the discal cell, the third small. The third longitudinal vein is 

 not forked, and there are three posterior cells. The hypopygium of the male is large 

 and bent under the abdomen, and is complicated in structure. The antennae are 

 simple, of three joints, with a terminal or dorsal bristle. 



The larvae are long, slender, and cylindrical, and live in the earth or in decomposing 

 vegetable matter. The pupae are free, or form cocoons ; their anterior stigmata in the 

 thoracic region are two elongated horny tubes. The flies have delicate, slender legs, 

 running about forwards, backwards, and sideways with great activity on the leaves of 

 plants. Most of them capture small Diptera or other insects, to even worms, with soft 

 bodies, and suck out their juices. " They are usually found in damp places covered 

 with a rich vegetation ; many are principally found on the leaves of aquatic plants, 

 on stories partly overflown with water, on dams, and near waterfalls ; some of them 

 are able to run rapidly over water, even when it is rippled by the wind ; others are 



