88 NATURAL II 1 STOUT. 



inch long, black, clothed with tawny hairs, with the wings greyish, tawny at the base and along the 

 front margin, the hinder margins of the abdominal segments gilded, and the legs tawny, with the 

 thighs black. 



FAMILY XII. EMPID^E. 



This is another family of Asiliform Flies, having an elongated body, a pointed abdomen, and a 

 horny proboscis. The head is globular, and the eyes of considerable size, meeting in the middle in 

 the males ; the crown of the head is not excavated as in the Asilidae ; the ocelli are distinct ; and the 

 antennae are of three joints, with a long and often jointed style or bristle at the apex. The proboscis, 

 which is horny and destitute of terminal lips, is generally of moderate length, and placed per- 

 pendicularly under the head ; sometimes, however, it is very long, and is then folded beneath 

 the breast. It contains three bristles, which are much finer than in the Asilidae. The wings 

 have a single complete cell on the disc. In their transformations the Empidte resemble the 

 species of the preceding families. 



Although much smaller than the Asilidae, the Empidae are equally predaceous in their habits, 

 feeding voraciously iipon insects of various kinds, but especially upon other Dipterous flies. They 

 may constantly be found flying or running about, carrying with them, transfixed by the bristles of the 

 mouth, insects quite as large as themselves ; and in some, forming the genus Hemerodronda and its 

 allies, the fore legs are even converted into prehensile organs, the coxae being as long as the thighs, 

 and the thighs thickened and spinous beneath. 



These, and many other species, all of small size, pursue their prey by running rather than on the 

 wing. They are found upon the leaves of shrubs and herbage, and their quickness of foot is expressed 

 in several of the generic names applied to them, such as Tachydromia and Ocydromia. These insects 

 are characterised by the structure of the antennae, in which the first joint is so small as to be 

 lost sight of; so that the organs apparently consist of only two joints, with a long bristle either 

 at the apex or on the back of the apical joint. 



The number of species in this family is very great, but they are chiefly confined to the 

 temperate or colder regions of the earth. They are very numerous in Europe. In default of 

 insect prey, or to vary their diet, they visit flowers and suck up the honey. Many species frequent 

 the neighbourhood of water, and some, such as the HUarcn, assemble i*", great swarms over the 

 surface of a stream and engage in most complicated aerial dances. 



The largest species of the family belong to the typical genus Empis, the female of one of 

 the best known British forms (Empis tessellata) attaining a length of nearly half an inch. This 

 insect is of an ash-grey colour, with three black stripes on the thorax, and the abdomen showing 

 a sort of tessellated pattern. It is common in spring. When paired, the females of this and 

 of many other of the larger species of the family are always found to be busily engaged in 

 sucking out the juices of some other insect. It seems probable that the male seizes the opportunity 

 of his intended partner being thus occupied to make his advances ; if her mouth was free he would 

 in all likelihood himself fall a sacrifice to her voracity. 



FAMILY XIII. ACROCERID^E. 



A few very curious flies constitute this family, the true position of which has often been a puzzle 

 to entomologists. They seem, however, to be most nearly related to the Humble-bee Flies, which 

 form the next family. They have the thorax and abdomen much inflated, the thorax especially being 

 much swelled above, and the head very small and globular, and placed very low down upon the 

 front of the thorax, so that it is more or less concealed when the insect is looked at from above. 

 The eyes are comparatively large, forming the greater part of the surface of the head, but there are 

 usually three distinct ocelli. The three-jointed antennae are very small ; the proboscis either long 

 and thin, and bent under the body, or entirely wanting ; the legs short and weak, with three pulvilli 

 to the tarsi ; and the halteres concealed beneath large, arched scales. The abdomen has only six 

 segments. 



The known species of this family are not numerous. Those possessing a long proboscis are 

 chiefly exotic, but in them this organ is usually longer than the body. Thus Lasia flavitarsis, a 

 Brazilian species of a steel-blue colour, with the scutellum and base of the abdomen violet and 



