308 NATURAL HISTORY OF ARTHROPODS. 



sonifaotion is the result of rubbing striated surfaces on the fifth abdominal segment 

 against the posterior edge of the elytra. In a dung-beetle ( Geotrupes) stridulation is 

 brought about by action of the hind edge of the third abdominal segment upon corru- 

 gated surfaces on the coxae of the posterior pair of legs. Stridulating sounds are pro- 

 duced by many other beetles, among which may be mentioned the following : Prionus, 

 by rubbing the rough inner side of the hind thighs against the lateral margin of the 

 elytra; Passalus by rubbing the acute edge of the ventral segments against the inner 

 edge of the elytra; Polyphylla, Anomala, Trox, Ligyrus, and Anthonomus by rub- 

 bing together corrugated surfaces of the metathorax and elytra. The three-striped 

 potato-beetle {Lema trilineata) and some other ChrysomelidoB stridulate. 



Luminous organs are found mostly in the family Lampyridae, but the larva of an 

 elaterid, probably of Melanactes, and the famous fire-fly of tropical America, the imago 

 of Pyrophorus noctilucans, another species of Elateridse, are luminous, and will be 

 further noticed when treating of their respective families. The mode of production 

 of light by beetles has been the subject of many experiments and researches. Pro- 

 fessor C. A. Young, the astronomer, has examined the spectrum of the light of a com- 

 mon fire-fly {Photinusf) and found that it was continuous, without lines, and that it 

 extended from Frauenhofer's line C, in the scarlet, to about F, in the blue, indicating 

 rays which affect the visual organs greatly without the production of much thermal or 

 actinic effect. 



Beetles live sometimes singly, sometimes gregariously, and inhabit almost every 

 conceivable substance and locality ; few are found in the ocean, or in salt-springs ; the 

 deepest caves are the habitats of blind species, of which those from the caves of Ken- 

 tucky and of the Pyrenees have been most investigated ; certain beetles are found in 

 nests of ants and termites, and others even in mummies ; there are water-beetles which 

 inhabit hot springs ; larvae of certain Telephoridas are often seen on snow ; a few beetles, 

 in their larval state, are parasitic in other animals, others inhabit galls on plants. 

 The food of beetles is as diverse as are their habitats. The rule has been considered 

 almost universal that Cicindelidae, Carabidte, Dytiscidae, Coceinellidas, and some other 

 families were carnivorous, while Hydrophilidae, Chrysomelidae, and others were herbivo- 

 rous. Late researches, especially dissections by Professor S. A. Forbes, have shown 

 that species of some of these families eat much more diversified food than had been 

 supposed previously. Of plants even the poison ivy and poison sumac (species of 

 Rhus) do not escape the attacks of insects. 



Beetles are attacked or destroyed by other organisms, chiefly skunks, birds, frogs, 

 toads, and many reptiles and fishes, among the vertebrates ; parasitic flies, wasps and 

 mites, and many predaceous arthropods, among the articulates ; numerous species of 

 internal parasitic worms, among which Gordius and Mermis — so-called hair-snakes — 

 play important parts ; many species of Gregarina, protozoan forms, especially common 

 in the intestinal canal of Tenebrionidae ; and finally, by parasitic fungi, which some- 

 times kill many beetles. 



To avoid some of these enemies, beetles often mimic their surroundings, plants, or 

 other insects. A common tortoise-shaped potato-beetle {Deloyala clavata), in New 

 England, looks so closely like excrescences on the leaves of the potato that few birds 

 would notice it. Another common North American chrysomelid ( Ghlamys plicata) 

 often deceives collectors of insects by its close resemblance to a piece of caterpillar's 

 dung on a leaf. H. W. Bates mentions that certain longicorns (Cerambycidfe) mimic 

 closely the ill-tasting and disagreeably odorous fire-flies (Lampyridae), even carrying 



