The Microscope and Biology. By W. Wesche'. 409 



at their bases, the insect is predaceous, as in Scatophagy Caricea,, 

 and many of the Cordyluridae. 



6. When the mouth-parts are as in Eule 5, except that the 

 teeth are transparent and less developed, the insect is a general 

 feeder, but is not predaceous, as in Calliphora, Musca, or Lucilia. 



7. When the labium is hardened into a style, or is geniculated, 

 and tracheal or traces of trachea? can be made out, but no vestiges of 

 teeth, the insect feeds on the juices or nectar of flowers, as in 

 Prosena or Siphona. 



8. When the labium is hardened into a style with no tracheae, 

 but more or less developed teeth, the insect is a blood-sucker, as 

 in Stomoxys, Glossina, or Melophagus. 



9. When special teeth or spines are found on the labrum or 

 hypopharynx the insect is predaceous, as in Dolichopus or 

 Phora. 



N.B. — The mouth-parts differ in the sexes of the last-named 

 family in several species that I have examined, but I do not 

 commit myself to the statement that it is so in all the species, or 

 that the females are predaceous and the males general feeders. So 

 far as my observations go I have taken a small acalyptrate Muscid 

 out of the mouth of P. concinna(?.) Mg. £ and have found the mouth 

 of P. incrassata Mg. <? simple, and armed as in Eule 9, in the 

 female. 



III. — The Contents of the Abdomen and the Food 



of Insects. 



a. Food. — Most preparations of the whole insect will show 

 food, or traces of food. When it is present in quantities, it is 

 often forced, by the pressure necessary in mounting, back into the 

 mouth, or through the weak membranes that are between the 

 plates of the abdomen, through the ovipositor, or through the anus, 

 giving an opportunity for examination better than that through 

 the chitinous segments of the body. Also the membrane alluded 

 to is often quite transparent, and permits a good view of detail, 

 even with an oil-immersion. My attention was first drawn to this 

 subject by a preparation of the female of the earwig (Forjicula 

 auricularia L.), which happened to have had a very full meal before 

 being killed. The abdomen was filled with a confused mass of 

 shreds of chitin, long-jointed stalks, and round reniform objects 

 which were pierced with a number of holes. I had made some 

 preparations of the aphides that I found in my garden, which also 

 was the place of capture of the earwig, and I recognised the 

 "jointed stalks" as the antennas and the reniform masses as the 

 eyes. I then looked for the tubes, characteristic of these insects, 

 which exude the " honey dew," dear to the Formicidae, and after 

 careful search I found a number. I examined other Forficuloz, 



