988 



INSECTS AND AKACHN1DA 



is an example, the antennae are never longer, and are commonly 

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

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

 the Lucanlj or stag-beetles, with the Scarabcei, of which the cockchafer 

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

 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, arid sometimes fold one over the other, thence 

 giving the name Lamelllcornia ; 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 

 antennae 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, Staphylimis, 

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

 Melolontha, Cetonia, Curculio, Necrophorus ; Orthoptera, Forficula 

 (earwig), Blatta (cockroach) ; Lepidoptera, Sphingidae (hawk-moths), 

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

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

 fying power ; Diptera, Culicidae (gnats of various kinds), Tipulidaa 

 (crane-flies and midges), Tabanus, Eristalis, and Muscidae (flies of 



various kinds). All the 



A T> larger antennae, 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- 

 tennae being thus preserved 

 together when not too 

 large. A curious set of organs is to be discovered in the 

 antennae 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, sometimes nearly 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 lamellae of the antennae of Melolontha present a great dis- 

 play of these cavities, which are indicated in fig. 737, A, by the 



FIG. 787. Minute structure of leaflike expan- 

 sions of antenna of MelolontJia : A, their in- 

 ternal layer ; B, their superficial layer. 



