988 



INSECTS AND ARACHNIDA 



is an example, the antenna? are never longer, and are commonly 

 shorter, than one of the pairs of palpi, whence the name of Palpi- 

 cornid is given to this group ; in the very large family that includes 

 the Lucani, or stag-beetles, with the Scwrabcei, of which the cockchafer 

 is the commonest example, the antenna? terminate in a set of lea Hike 

 appendages, which are sometimes arranged like a fan or the leaves 

 of an open book (fig. 736), are sometimes parallel to each other like 

 the teeth of a comb, and sometimes fold one over the other, thence 

 giving the name Lametticornia ; whilst another large family is 

 distinguished by the appellation Longicornia, from the great length 

 of the antenna?, which are at least as long as the body, and often 

 longer. Among the Lepidoptera, again, the conformation of the 

 antenna? frequently enables us at once to distinguish the group to 

 which any specimen belongs. As every treatise on entomology con- 

 tains figures and descriptions of the principal types of conformation 

 of these organs, there is no occasion here to dwell upon them longer 

 than to specify such as are most interesting to the microscopist : 

 Coleoptera, Brachinus, Calathus, Harpalus, Dytiscus, Staphylinus, 

 Philonthus, Elater, Lampyris, Silpha, Hydrophilus, Aphodius, 

 Melolontha, Cetonia, Curculio, Kecrophorus ; Ort/tnptera, Forficula 

 (earwig), Blatta (cockroach) ; Lepidoptera, Sphiiigida? (hawk-moths), 

 and Noctuina (moths) of various kinds, the large 'plumed ' antenna- 

 of the latter being peculiarly beautiful objects under a low magni- 

 fying power ; Diptera, Culicida? (gnats of various kinds), Tipulidse 

 (crane-flies and midges), Tabanus, Eristalis, and Aluscida? (flies of 



various kinds). All the 

 larger antenna?, when not 

 mounted ' dry ' as opaque 

 objects, should be put up in 

 balsam, after being soaked 

 for some time in tur- 

 pentine ; but the small 

 feathery antenna? of gnats 

 and midges are so liable 

 to distortion when thus 

 mounted that it is better 

 to set them up in fluid, the 

 head with its pair of an- 

 tenna? being thus preserved 

 together when not too 

 to be discovered in the 



PIG. 737. Minute structure of leattike expan- 

 sions of antenna of Mi Inluiill/n : A, their in- 

 ternal layer ; B, their superficial layer. 



large. 



A curious set of organs is 

 antenna? of many insects, which have been supposed to constitute 

 collectively an apparatus for hearing. Each consists of a cavity 

 hollowed out in the horny integument, sometime.-, nearlv spherical, 

 sometimes flask-shaped, and sometimes prolonged into numerous 

 extensions formed by the folding of its lining membrane ; the mouth 

 of the cavity seems to be normally closed in by a continuation, of this 

 membrane, though its presence cannot always be satisfactorily deter- 

 mined ; whilst to its deepest part a nerve-fibre may be traced. The 

 expanded lamella? of the antenna- of .l/<'/u/<>, >//><> present a great dis- 

 play of these cavities, which are indicated In tig. 7-'>7. A. by the 



