The subfamily Cassidinae in old sense, commonly named “tortoise beetles”, is a part of the large family Chrysomelidae (leaf or plant beetles). They are almost world-wide in distribution, though they have a much greater diversity in the tropics, especially tropical South America. They are scarce in temperate regions of North America and Australia and abundand in temperate Euroasia. The last catalogue (Borowiec 1999) lists 2760 species (except the tribe Imatidiini classified traditionally within Cassidinae but recently transferred to the tribe Cephaloleini of the subfamily Hispinae).

The subfamily was proposed by Gyllenhal (1813) as the group Cassidites for the chrysomelid genus Cassida. Chapuis, in Lacordaire (1875), proposed the group Cryptostomes for Cassidinae and Hispinae and divided the cassidoid beetles in to 17 groups. An Austrian entomologist, Franz Spaeth, one of the greatest specialists in the subfamily, the author of the first world catalogue of Cassidinae (Spaeth 1914g), ignored this subdivision and recognized only three unnamed tribes within the Cassidinae, but in several further papers (Spaeth 1923, 1929b, 1942) he adopted most of the tribes proposed by Chapuis, usually without comments. Shortly before World War II Spaeth was engaged in preparing a manuscript on the Cassidinae for publication in Wytsman's Genera Insectorum, with a key to all the world's species. The manuscript was completed sometime in 1942. Unfortunately, it was almost completely destroyed when the printer's premises in Vienna were damaged by Russian bombing. Only proof-copy of the first volume of the work and some sheets of the manuscript were saved. Hincks (1952) based on this proof-copy prepared a posthumous paper with a review of the 19 tribes (in a form of an identification key) and a list of all genera proposed and authorised by Spaeth (including descriptions of several new genera and nomenclatorial changes), with designation of type species for each genus. His system of the subfamily was adopted by Seeno and Wilcox (1982) in the list of the world genera of Chrysomelidae. Hincks, Seeno and Wilcox overlooked the fact that Monros and Viana in 1947 synonymized the cassidoid tribe Himatidiini with the hispoid tribe Cephaloleiini. Most later authors commonly accepted Spaeth's system with corrections by Hincks, Seeno and Wilcox.

The only author who proposed a completely different system of the group was Chen (1973). He created a new superfamily Cassidoidea with four families: Cassididae (in old sense, with four tribes of uncertain position: Hemisphaerotini, Spilophorini, Delocarniini and Imatidiini), Anisoderidae, Hispidae, and Callispidae. Later Chen et al. (1986) included cassidoid beetles in the family Hispidae as an independent subfamily.

Recently, a tendency for a reduction of traditional tribes of cassidinae is observed. Riley (1986) synonymized the tribe Charidotini with the Cassidini. Medvedev and Eroshkina, based on larval characters and bionomics, transferred the tribe Notosacanthini from the Cassidinae to the Hispinae. Borowiec (1995a) in the most complete phylogenetic analysis of the subfamily proposed only 11 tribes, including Notosacanthini as a cassidoid group. He also suggested that Cassidinae are polyphyletic, that the division of the group Cryptostoma into two subfamilies: Hispinae and Cassidinae is artificial, and proposed the name cassidoid Hispinae for the tribes of Spaeth's system (except Imatidiini). This point of view was considered by Reid (1995) in his classification of Chrysomelidae using cladistic methods. Świętojańska (2001c) restored the tribe Aspidimorphini and placed it within the most specialised cassidoid beetles. Finally, Staines (2002) proposed the name Cassidinae for all Cryptostoma members. Both Cassidinae and Hispinae were proposed by Gyllenhal (1813) in the same paper, but Cassidinae appeared on p. 434 while Hispinae appeared on p. 448. The name would still be Cassidinae if one applied the determination of the first reviser [ICZN Article 24.2] (Chen 1940). Staines (2002) fused the tribe Spilophorini, classified traditionally in Cassidinae, with the tribe Oediopalpini, classified traditionally in Hispinae.

In this manual Borowiec's (1995) system was adopted with some modifications, with Aspidimorphini, Eugenysini, and Goniocheniini as independent tribes. Only the genera of Cassidinae of old sense have been included, with two genera traditionally placed in the tribe Spilophorini. From the tribe Imatidiini, actually synonymised with hispine tribe Cephaloleini, only species traditionally placed in cassidine genera have been included.

Cassidinae feed on 32 plant famillies, but Convolvulaceae and Asteraceae are preferred. Of other families only Arecaceae, Boraginaceae, Caryophyllaceae, Chenopodiaceae, Lamiaceae and Solanaceae offer more than 20 host plant species. Three tribes: Delocraniini, Hemisphaerotini, and Spilophorini occur only on monocotyledons, other exclusively on dicotyledons. Only larvae of the tribe Notosacanthini are leaf miners, other are exophagous.

Cassidinae are one of the few groups of insects in which the females construct papery oothecae to protect their eggs. The oothecae exist in many different forms, often have a smaller or greater amount of the mother’s feces placed on top for further camouflage.

The exophagous larvae usually have a caudal appendage with a muscular attachment, located above the anus. The anus is highly muscular and telescopically protrusible. This is correlated within the ability to attach the feces to various parts of the accumulated exuvia, or to the caudal furca in the first instar (see fecal shield of Aspidimorpha sanctaecrucis, Chiridopsis bipunctata and Aethiopocasis manubialis). Sometimes larvae have no caudal exuvia or fecal shields, occasionally they have no or strongly reduced caudal forks (Delocraniini and Hemisphaerotini). Exophagous larvae of Cassidinae have a very characteristic appearance, distinct from other chrysomelid beetles. The larvae always have lateral processes or spines arranged along the sides of the thoracic and abdominal segments (see figure of Chiridopsis rubromaculata). The normal arrangement for each side is three on the prothorax, three on the mesothorax, two on the metathorax, and one of each abdominal segment. They continue along the sides of the abdomen generally to the eight segment, and the caudal furca or supraanal process represents, at least in anlogy, the fused process of the ninth abdominal segment. In primitive tribes sometimes there are only two mesothoracic processes or spines. Larvae of most species are solitary, but cycloalexy was observed in several species from Central and South America, South Africa and the Oriental Region (see photos of cycloalexic larvae and pupae of Aspidimorpha miliaris). In some species of the tribes Eugenysini and Stolaini maternal care has been reported (Windsor and Choe 1994, Chaboo 2002) - see Acromis sparsa.

The pupae are in some respects very similar in appearance to the larvae (see pupa of Chiridopsis rubromaculata). They are dorsoventrally flattened, have fringing appendages around the borders and usually have the same exuvial-fecal armature with the addition of exuvia of the fifth instar. The pupae usually possess caudal furcae, which in some cases appear to be separated at their insertions. The lateral appendages of the abdomen frequently are in the form of broadly expanded plates with fringing spinules, or appear as long, sinuous spines. The appendages of the prothorax usually consist of numerous short filaments or a few longer ones, but sometimes they are entirely lacking. The meso- and metathoraces have wings substituted for the larval appendages.

Larvae and pupae of Notasacanthini are distinct because of their mining mode of life. They are more similar to larvae of many members of the Hispinae rather than to members of the true Cassidinae (see larva and pupa of Notosacantha vicaria). At least in one species of Notosacantha larvae before pupation form a different pupal mine.

Adults are exclusively exophagous. In many species, especially of the tribes Aspidimorphini, Cassidini, and Physonotini, live specimens distinctly differ from dried specimens in collections. Live specimens have distinct metallic tint of an ephemeral nature. It is a result of a combination of structural and functional effects, infolving both reflection of light rays from numerous semitransparent or completely transparent layers in the cuticle, and presence of body fluid between the minute layers (Onslow 1921, Mason 1929). This fluid is lost with desiccation following death and the iridescence disappears. Some species have an ability to change the intensity of the iridescence by widening or narrowing the spaces between the layers of cuticle. Fortunatley, soaking dried specimens in water or even in alcohol, the golden iridescence can be restored to a greater or lesser degree, but only to be lost again with re-desiccation. Colour photos in the manual based on dried specimens, only few species have been presented based on live specimens( e.g. Charidotella sexpunctata, Coptocycla dorsoplagiata, Deloyala cruciata, and Helocassis clavata).

Sexual dimorphism occurs in many species, but usually is more pronounced in the more primitive groups. In the tribe Stolaini the degree of sexual dimorphism is correlated with the degree of male competition in sexual behaviour. In the manual photographs of both sexes are presented for species with distinct dimorphism (where both were available). Many species are polymorphic and produce various colour forms. In the manual more than one photograph is presented for polymorphic species, but in extremely polymorphic species only few of the numerous colours aberrations are shown, especially representing extremes of variability.

List of tribes
List of species
List of genera
List of photos