Objects for the Microscope. 141 



These flies are found amongst water-plants ; they are 

 black, shining, slightly metallic, with bright red legs ; the 

 halteres, also red, with a whitish band. Thorax with four 

 black stripes ; wings gray, with a lurid tinge in front. 



SEPSIS. 



The pretty little fly which we find upon our laurels, 

 walking about with raised and quivering wings. The larvae 

 feed on decaying matter. 



The antennae are drooping and short, with the third joint 

 oval and larger than the first or second ; the arista bare. 



Proboscis broad and large ; the wings simply veined, 

 but very delicate and beautiful, and with a black spot at 

 the tip, without alulae. The legs are remarkable for the 

 large spines in the fore-femora of the male, and for the 

 spiny meta-tarsi. 



In all flies, as a rule, the fewer the veins the smaller the 

 body, and the more sluggish the flight ; the comparison 

 between the veins of Leptis, Tabanus, and Phora, or 

 Sepsis, will prove this. 



The Sepsis wing has a costal vein running quite round 

 the tip of the wing, and ending on the hind border ; sub- 

 costal ending before one-third of the length ; mediastinal 

 ending before half the length ; radial ending near the tip 

 of the wing ; cubital ending quite at the tip. There are 

 two transverse veins. 



This list of the Diptera, though by no means complete, 

 is sufficient to show how very instructive and interesting 

 these preparations are, and to encourage the young ento- 

 mologist to mount insects in this way for himself. The 

 method is easy, but requires patience and experience. 



Soak the insects in liquor potassi for a longer or shorter 

 period, impossible to fix, because it varies necessarily with 

 the size and texture of the insect. A beetle may require 

 months, a fly but a few weeks or days, to render it trans- 

 parent, by dissolving its inward parts, and giving flexi- 

 bility to its integument. It is then washed in cold water, 

 and laid out upon a glass slide in the desired position. 

 When perfectly dry it should be soaked in oil of turpentine, 



