140 Objects for the Microscope. 



tubes, and that the blood is conveyed forward by the out- 

 ward ones, and backward by the intermediate one ; also 

 that there is a secondary heart, at the extremity next the 

 thorax, for the purpose of causing the reflux." 



BORBORUS EQUINUS. 



These are very abundant everywhere in rank grass, and 

 near decaying vegetable matter, upon which the larvae feed. 

 They are small black flies, remarkable for their thick fleshy 

 labium, and a broad bellying sheath below, which should 

 be seen in profile. Antennae rather distant, short, and tur 

 outwards with a long slender arista ; the first joint so small 

 as to be scarcely perceptible, the second nearly as large 

 as the third, which is obliquely compressed and ciliated. 

 The legs are long, and fore-femora thickened ; there is a 

 curious spine at the end of the hind tibia, and the tarsi 

 are short and broad. The wing, being very simply veined, 

 is an easy study ; the chief mark of this family being in 

 two small areolets near the base of the wing, close to the 

 hind border, which are called anal areolets, and in this 

 wing they are complete. The discal transverse vein is also 

 near the border ; it joins the prcebrachial and pobrachial 

 together, the latter does net continue beyond it. The radial 

 and cubital are branches from one common vein at the base. 



There is a full account of this species and its larvae in 

 the ' Entomological Magazine ' (vol. iii. p. 323). 



SEPEDON. 



A most beautiful specimen for the shape of the antennae 

 and the structure of the tongue. The wing closely resem- 

 bles that of Borborus, the same transverse veins and anal 

 areolets ; but the antennae separate the genera entirely. 

 Instead of the short second joint in Borborus, that of 

 Sepedon is very long and spiny, with a conical and convex 

 third joint, from which springs the three-jointed arista. 



The labium is set round with double hooks and curiously 

 dotted, a most interesting variety in the proboscis of flies. 



The legs are rather long, hind femora thickened, and 

 armed with a double row of spines. 



