Tlie Microscope and Biology. By W. Weschi. 407 



abdomen, modified into sharp hooks. Lauxanea aenea Fin. has 

 the same. These structures are peculiar, as usually the chitinous 

 plates are altered. They are undoubtedly " secondary sexual," 

 and present degrees of development in those species observed ; 

 They are very marked in S. fasciata, might easily escape notice in 

 S. apicalis and L. cenea, while they are absent in S. lupulina F. 

 and Lauxanea bilineata Hutton (N. Zealand) and L. decora Schiner 

 (S.E. Australia). 



Borborhle. The membrane of the abdomen in B. equinus L. 

 is studded with short sharp spines, but not close to each other in 

 the contact areas, as in the Sapromyzida? ; the corresponding part 

 in the male is nearly bare, though the plates on the ventral side 

 of the abdomen are thickly covered with seta?. Sphasrocera sub- 

 sultans F. has similar modifications. 



HiPPOBOSCiDiE. H. equina L. has large lateral spined tubercles 

 on each side of the vagina, as well as two spiny patches on the 

 dorsal side, near the posterior end of the abdomen ; the whole of 

 this part is much more sharply spined than in the male. 



Olfersia tasmanica Wesche, a Tasmanian insect, parasitic on 

 the Wallaby, has tubercles in the same places, but they are armed 

 with long delicate spines. 



II. — The Mouth-parts. 



The majority of insects are provided with a strong pair of 

 biting or crushing jaws (mandibles), which break up their food and 

 enable the smaller jaws (maxilla?) to seize it, and with the aid of 

 the labium transmit it down the gullet till it reaches the gizzard. 

 The three principal orders whose trophi most markedly differ from 

 this scheme are the Hemiptera, Lepidoptera and Diptera, and the 

 microscopist who is familiar with these four types can already do 

 much in classifying his preparations. The Hemiptera can be 

 easily recognised by their " beak " : a sharp case (labium) which 

 contains fine delicate lancets (mandibles and maxilla?) and is 

 usually turned in under the thorax. The Lepidoptera have their 

 maxilla? modified into a long double tube, which is carried curled 

 up like a watch-spring. The Diptera are distinguished by the 

 presence of trachea? on the labium. In the Culicida? (gnats) and 

 certain parasitic forms this character may fail, but high powers will 

 show traces of their presence, or of their presence in the past. 

 Mandibles that bite or crush will never be found, though their 

 representatives are present in certain families ; but in the trophi 

 there is such a wide range of variation, and such alteration of 

 detail, that from a study of this part alone a judgment can be 

 formed of the habits and food, and in the majority of cases of the 

 place in the scheme of classification. I have treated this subject at 



