Beetles eat almost any substance of organic origin: live plants and live animals, wood, paper, fabrics, wool, leather, fur, meat, fish, etc.
By food object insects are divided in the first turn into phytophagans (plant eaters) and zoophagans (animal food eaters). It has been long since fungi are not classified with plants, but are placed in a separate kingdom; it would be more correct, therefore, to separate mycetophagans (consumers of fungi) from phytophagans. It is necessary to separate also saprophagans feeding on dead (and usually decomposed) organic substrate - decomposed plant and animal remnants. As with an attempt to classify complex phenomena contradictions arise and different points of view exist as regards determining types of feeding. This concerns saprophagans in the first turn. Feeders on wood that is dead but is still retaining its structure are usually classified with phytophagans. However, if insects consume decomposed wood, they are regarded as saprophagans. In classification of dead animal feeders decomposition is usually not taken into account. Dead matter eaters consuming both complete and strongly decomposed cadavers are more often regarded as saprophagans.
In classifications of feeding types there is usually no reference to special diets that are difficult to classify with any of the three main types. It is not quite clear, for example, where to place consumers of paper, textiles or wax?
Particularly diverse are phytophagans feeding on all parts of living plants, dead plants and even woodwork. For almost every group of phytophagans there is a special name determined by their diet. But many subdivisions of phytophagans intersect being defined by different classification bases. Traditionally used as such bases are life forms of plants fed on (hence - dendrophagans, mycetophagans, :) and their organs (hence phyllophagans, anthophagans). To establish simple subordination of such groups is very difficult. Therefore we had to repeat some names in different parts. Moreover it is important to take into account that many species of beetles at the same time belong to several groups by formal classification.
Up to 2001 the classification given below remained on the site without changes and I only had to add missing terms on advice of my colleagues and visitors of the site. The first serious change was to be made at the site in the part of zoophages on advice of S.S. Izhevsky. In 2002 A.G. Kirejtshuk suggested to make serious changes. He insisted on placing mycetophagans in a higher taxon and separating different phyla of those. Our permanent author Dmitry Telnov offerred a number of comments and suggestions. On his advice we erect the rank of dendrophagans, introduce repetitions, but eliminate a number of cross-repetitions. The classification, that was merely compilatory becomes a work of several authors. It is quite possible that imminent contradicitions cannot be reconciled within the framework of one classification; new competitive classifications will appear. The editorial board of the site would be happy to receive any suggestions. The style of internet publications permits such decisions. Therefore we insistently invite every one interested in search for truth to send not only comments, but also their versions of the classification as whole. There is only one condition: terms and types of feeding should be included in the scheme. Our collection of terms ending with "phagan" is unique already. There is hardly any publication where one can find all the names we are interested in. It would be a pity to reduce it.
One more working comment. Because the classification in almost any respect may be applied not only to beetles, but also to insects we would not like to exclude variants logically justified, but unknown among beetles (e.g. hemophagans or aphid parasitoids). Therefore it is now better to regard this scheme, not as the one established for known types of feeding of beetles, but as a kind of theoretical one applicable to other insects and being of prognostic nature.
Four-level classification of types of feeding of beetles and other insects may be proposed as a working variant.
There are no harmful or beneficial beetles for the nature. But when food requirements of beetles interfere with interests of humans there appears the concept of harmful beetles (feeding on plants important to humans) or beneficial insects (destroying enemies of humans). There are pages devoted to beneficial and harmful insects.
A.L. Lobanov, 2002
Кривошеина Н.П., Зайцев А.И. 1989. Филогения и эволюционная экология двукрылых насекомых. В: Итоги науки и техники. Энтомология. Том 9. Москва, 1-166.