6o 



INSECTS. 



proboscis, and prey upon insects of various kinds, often seizing and carrying off 

 butterflies, much larger than themselves. The general form of the members of 

 this family is shown in Fig. 1 of the annexed illustration, representing Dioctria 

 oelandica, a species from the island of Oeland, off the coast of Sweden, with 

 a shining black body, and wings of the same colour. Many species of the genus 

 Asilus are found in Britain, but the largest and handsomest of all is the hornet 

 robber-fly (A. crabroniformis), measuring upwards of an inch in length, and of a 

 yellowish colour variegated with black, there being four stripes of the latter colour 

 upon the thorax, and a broad transverse band across the base of the abdomen. 

 Some of the tropical members of the family are far larger, those belonging to the 

 genus Mydas, from South America, being scarcely surpassed in dimensions by any 

 member of the order. The fly represented in 2 of the illustration is the tesselated 

 empis (Empis tessellata), belonging to the family Empidce, the species of which 



are predaceous like the Asilidce, 

 and resemble them in form, but 

 differ in certain structural details 

 which need not be dwelt upon. 

 The tesselated empis the 

 largest member of the group 

 found in Britain is ashy grey 

 in colour, and has its abdomen 

 ornamented with a chess-board 

 pattern. As Dallas expressed 

 it, " 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 were free he would in all likelihood 

 himself fall a sacrifice to her voracity." 



The families of short-horned, straight -seamed flies hitherto 

 considered resemble each other in the fact that the larvae live in the 

 earth, and feed upon the roots of grass or other vegetable matter, while the adults 

 prey upon other animals, whose blood they suck. But in the bee-flies (Bomby- 

 liidce) so called from the likeness in hairiness and shape they present to humble- 

 bees the larvae, so far as known, live parasitically on other insects, attacking 

 grasshoppers, caterpillars, etc., while the adults suck the juices of flowers. The 

 genus Bombylius is represented in England by a small number of species, although 

 in the tropics there are large numbers of forms. In all the thick, fat body is 

 covered with long yellow hairs. The wings are powerful ; and the head is furnished 

 with a long proboscis, which is thrust into blossoms while the insect (No. 8 on p. 65) 

 stays poised in mid-air, like a hawk-moth when similarly occupied. The black-and- 

 white bee-fly (Anthrax semiatra) is mostly of a black tint, and clothed with hair 

 of the same colour ; but the hairs on the front part of the thorax and abdomen take 

 a yellowish tinge, the wings, as shown in the illustration, being black in the basal 

 half but clear elsewhere. These insects may be seen on the wing in dry, sunny 

 spots, stopping from time to time to suck a flower, or rest upon a stone, and seeking 



ROBBER-FLIES. 



1, Dioctria oelandica ; 2, Empis tessellata (nat. size). 



