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 
oelctndica, 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 tessellatci), belonging to the family Empidce, the species of which 
are predaceous like the Asilidcc, 
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 
Bee-Flies. . . 
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 Bomby lius 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 wiilgs 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). 
