AT THE MICROSCOPE. 115 



Gizzard of Small Foreign Cockroach (PI. XV., Figs, i — 2). — 

 This is so interesting a specimen that one would wish to see other 

 examples in which the relations of the parts have been less dis- 

 torted, as also to ascertain the correct name and habitat of the 

 insect whence it has been taken. The number six is so usual in 

 the division of insect gizzards that I am led to ask if it be not 

 possible that in so delicate a dissection one of the segments may 

 have disappeared ? I should, in making such a preparation, be 

 content with carefully cutting down one side, laying the parts open 

 gently, washing, and then putting up in glycerine jelly. From the 

 appearance of the parts here, I can hardly be wrong in believing 

 it to have been submitted to the action of potash, and in that way 

 seriously injured. It is not unusual to find in a family 

 of insects some species having carnivorous habits, although the 

 majority of the species composing it are phytophagous. Now, in 

 the nature of their food, the Blattae are known to be mostly 

 omnivorous, and I imagine, looking at the specimen before us, that 

 its possessor was of insectivorous habits, and that soft larvae most 

 likely formed its prey. The gizzards of insects form, when 

 systematically examined, a most interesting study. [Interesting 

 notes on the " Gizzard of Beetle" will be found in Vol. IV., p. 

 256. — Ed.] 



Green Flies. — These beautiful flies are examples of one of the 

 ChalcididcE, parasites on one of the Gall-insects. Some of these 

 occasionally appear on our windows in great numbers in the 

 autumn. They are not, properly speaking, " Ichneumon-flies." 

 There is an ovipositor in the females, but it is short, and con- 

 cealed in its sheath ; the minuter parts are scarcely displayed in a 

 way to render identification safe. The gorgeous colours seen on 

 the wings are (like the prismatic hues of a soap-bubble) a purely 

 optical effect of their extreme thinness ; to this display of colour 

 the term " iridiscence " [iris, the rainbow) is applied. There 

 are no scales on the wings of any of the Hymenoptera. The 

 minute hooks which unite the two wings in flight are well shown 

 in one or two examples, and recall in their simplicity the very 

 similar arrangement present in the wings of Aphides. They con- 

 trast well with the numerous powerful hooks on the posterior pair 

 of wings in Bo?nbus ierrestris. 



TuFFEN West. 



