308 NATURAL HISTORY OF ARTHROPODS. 



sonifaction is tlio result of nibbiuo; striated surfaces on tlie fifth abcloiiiinal segment 

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

 brought about by action of the hind edge of the third abdominal segment u])on corru- 

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

 duced by many other beetles, among ^-hich may be mentioued the following : frionus, 

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

 elytra; Passcthis by rubbing the acute edge of the \entral segments against the inner 

 edge of the elytra; PohjplujJhi^ Anoinaki, Tro.i; Li(jijni.% and Anthotwmict by ruli- 

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

 potato-beetle {Lema trilineata) and some other Chri/sotaelklw stridulate. 



Luminous organs are found mostly in the family Lampyrid;e, but tlie larva of an 

 elaterid, jirobably of Melaiuictes, and the famous tire-Hy of tropical America, the imago 

 of Pi/rophorHS noctihicans, another species of Elateridae, are luminous, and will be 

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

 of light by beetles has been the sul)ject of m.any exjieriments and researches. Pro- 

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

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

 exten<led from Frauenhofer's line C, in the scarlet, to about F, in the blue, indicating 

 ravs 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 tlie 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 ; larva' of certain Teleiihorida^ are often seen on snow ; a few beetles, 

 in their larval state, are parasitic in other animals, otliers inhabit galls on jilants. 

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

 almost universal that Cicindelida?, Carabida^ Dytiscidw, Coccinellida?, and some other 

 families were carnivorous, while Hydroi)hilidfe, 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 Vjeen 

 suj)posed previou.sly. Of plants even the ]iiiis<in ivy and jioison sumac (sj)ecies of 

 Mhus) do not escape the attacks of insects. 



Beetles are attacked or destroyed by other organi>iiis, chiefly skunks, birds, frogs, 

 toads, and many rej>tiles and fishes, among the vertebrates; parasitic flies, wasjis and 

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

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

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

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

 times kill many beetles. 



To avoid some of these enemies, beetles often mimic their surnuindings, 2)lants, or 

 other insects. A common tortoise-shaped potato-l)eetle (IM/oi/a/a cktrata), in IS'ew 

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

 would notice it. Another common Xorth American chrysomelid ( Chlamys plicata) 

 often deceives collectors of insects by its close resemblance to a piece of c.aterj)illar's 

 dung on a leaf. II. W. Bates mentions that certain longicorns (Cerambycida^) mimic 

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



