LeSage Laurent, 1991

Coccinellidae (Cucujoidea) or The Lady Beetles, Lady Birds, P. 485-494.

In: Stehr Frederick W. (Ed.), Immature Insects, Vol. 2. Kendall/Hunt Publishing Company, Dubuque, Iowa. 975 p.

Relationships and Diagnosis: The Coccinellidae, commonly known as ladybird beetles, belong to the superfamily Cucujoidea, and are closely related to the Endomychidae and Corylophidae (van Emden 1949; Crowson 1955). There are about 490 genera and 4200 world species (Sasaji 1971) of which about 425 are known from the United States and Canada. Coccinellid larvae usually have a reduced mola on the mandible (absent in Epilachninae) (figs. 34.593-34.599), a gular area between the labium and the thorax (fig. 34.586), and the median epicranial stem (coronal suture) is absent in most genera (figs. 34.583-34.585). The most distinctive characteristics of coccinellid larvae are a great development of the body armature into setose processes in most tribes, a campodeiform and usually brightly colored body, and mandibles of a predaceous type in most tribes (acute at apex). Except in Epilachnini and Psylloborini, they are usually very active predators.

Many galerucine and some alticine larvae in the Chrysomelidae superficially resemble larvae of coccinellids. However, chrysomelid larvae have short legs, none or only 1 pair of stemmata, no setose processes on the body (rarely with processes covered by fine setae) and the mandibles lack a mola, whereas coccinellid larvae which may be mistaken for chrysomelid larvae have long legs, 3 pairs of stemmata, large setose body processes covered by robust setae, and a mandibular mola.

Biology and Ecology: It is not possible to treat here in detail the bionomics and ecology of Coccinellidae. See the excellent reviews by Balduf (1935), Hagen (1962), and Hodek (1967, 1973).

The eggs, usually oval or spindle-shaped, vary in colour from yellowish to reddish orange, and are mostly laid in clusters on the underside of leaves or in bark crevices in the vicinity of prey.

In general, there are 4 larval instars which last about 10 days each, but with great variation according to species and ecological factors. A unique feature among coccinellid larvae is the presence of secretory structures that produce a visible coating of waxy threads in the larvae of several tribes; these probably have primarily a defensive role against predators (Pope 1979). Cannibalism is frequent in coccinellid larvae and increases the chances of survival when there is a very low density of prey (Hodek 1973; Dimetry 1976). Larvae perceive their prey only by contact (Fleschner 1950; Putman 1955a, 1955b; Dixon 1959; Kaddou 1960; Frazer et al. 1981). With the development of biological control programs, attempts have been made to rear larvae on artificial diets or dried food. Several recent experiments gave excellent results (Smith 1960; Fisher 1963; Shands et al. 1966; Hodek 1973 (review); Kariluoto 1980).

Different types of pupae occur in Coccinellidae. Coccinellinae and Sticholotini have naked pupae attached by the cauda to the substrate. Pupae of the Chilochorini and Noviini are partly covered by the skin of the last larval instar, and the Hyperaspini and Scymnini have pupae completely covered by larval skins. The pupa is not entirely immobile; if irritated, the head region is raised several times by upward jerks of the body.

The number of generations varies greatly according to species and latitudes; types of voltinism were summarized by Hagen (1962). Perhaps the most fascinating phenomenon coccinellid adults display is the formation of aggregations. Species involved usually feed mostly on aphids, exhibit long dormancy or diapause periods, and mate at the aggregation site before the beetles disperse or migrate (Hagen 1962; Hodek 1967, 1973; Benton & Crump 1979; Lee 1980).

The role of coccinellids in natural control has been demonstrated many times. Various interrelated factors affect the ability of coccinellids to check pest infestations. However, it seems that the most important factor involved, temperature, was probably also the most neglected in theories of insect predation (Baumgaertner et al. 1981).

Since the bionomics, general habitus and food preference are generally distinctive for each tribe, a key to tribes is presented below, followed by a short synopsis of each tribe.

Body Armature: Gage's terminology (Gage 1920) is generally followed for different structures on the body of larvae. A seta (fig. 34.610) is situated directly on the body surface; a chalaza is a seta mounted on a small base (fig. 34.611). A verruca or tubercle is a small protuberance covered by setae instead of chalazae (fig. 34.612). A struma appears to be a mound-like projection of the body-wall upon which are situated a few chalazae (fig. 34.613). Aparascolus (fig. 34.614) is an elongate process covered by chalazae, but less than 3 times as long as wide. A scolus (fig. 34.616) is a branched projection, usually more than 5 times as long as wide; each branch bears at its distal end a single stout seta. A sentus (fig. 34.615) is a projection of the body-wall which is not branched like a scolus but bears stout setae on its trunk. Larvae may have structures intermediate between scoli, senti, parascoli or strumae.

1.       Body with scoli (figs. 34.570, 34.616);
            mandible without mola (fig. 34.597)                                    Epilachnini
         Body without scoli (figs. 34.572-34.575); mandible with mola (figs. 34.593-34.596)  2
2(1).    Epicranial suture present (figs. 34.582, 34.583, 34.585)                            3
         Epicranial suture absent (fig. 34.584)                                             11
3(2).    Epicranial suture V-shaped (fig. 34.585)                                            4
         Epicranial suture U-, Y-, or lyre-shaped (figs. 34.582, 34.583)                     6
4(3).    Antennae large, conspicuous, second and third segments elongate
            (fig. 34.600)                                                          Scymnillini
         Antennae small, inconspicuous, second and third segments short (fig. 34.585)        5
5(4).    Mature larvae small, less than 3 mm (fig. 34.575);
            tibiotarsi with a pair of apical flattened setae (fig. 34.618);
            maxillary palps 3-segmented (fig. 34.608)                             Sticholotini
         Mature larvae larger, more than 6 mm (fig. 34.574);
            tibiotarsi with several apical clavate setae (fig. 34.617);
            maxillary palps 2-segmented (fig. 34.609)                                  Noviini
6(3).    Pores of repugnatorial glands present in the coria between abdominal segments on 
            the antero-lateral margin (fig. 34.587);
            body always with long senti (figs. 34.587,34.615)                     Chilochorini
         Pores of repugnatorial glands absent, body usually with strumae (fig. 34.613) 
            or parascoli (fig. 34.614), rarely with senti (fig. 34.615)                      7
7(6).    Apex of mandible simple (fig. 34.594)                                               8
         Apex of mandible bidentate (figs. 34.596, 34.599)                                  10
8(7).    Body densely covered with fine hairs andfyong setae (fig. 34.624);
            tibiotarsi slender and narrowing apically                               Serangiini
         Body covered with few large setae located on tubercles or strumae
            (figs. 34.623, 34.573);
            tibiotarsi short, stout, and truncated apically (fig. 34.588)                    9
9(8).    Three pairs of conspicuous, pigmented, sclerotized plates (strumae) on abdominal
            segments 1-8 (fig. 34.623); body not covered by wax-like secretions     Stethorini
         Three pairs of inconspicuous, not pigmented, tubercles on abdominal segments
            1-8; body covered by wax-like secretions                        (in part) Scymnini
10(7).   Few large chalazae on disk or posterior margin of abdominal segment 9
            (fig. 34.622); body dull yellowish; third antennal segment always 
            well-developed and cupola-like (fig. 34.602)                           Coccidulini
         Numerous setae and/or small chalazae on abdominal segment 9 (fig. 34.621);
            body brightly colored with black, brown, red, yellow or orange; third antennal
            segment usually much reduced,
            antenna appearing 2-segmented (fig. 34.606)                           Coccinellini
11(2).   Apex of mandible multidentate (fig. 34.595);
            body without wax-like secretions                                      Psylloborini
         Apex of mandible simple (fig. 34.594);
            body covered with wax-like secretions                                           12
12(11).  Labial palp very small, dome-shaped, 1-segmented (fig. 34.592)            Hyperaspini
         Labial palp normal, 2-segmented (fig. 34.591)                      (in part) Scymnini

Unlike other coccinellids, the Epilachnini (Epilachninae) have an unusual porcupine-like appearance (fig. 34.570), and are phytophagous. Furthermore, in this tribe the mandible (fig. 34.597) lacks a mola and has a multidentate apex. Epilachna borealis (Fabricius), the squash beetle, attacks squash and pumpkins, and E. varivestis (Mulsant), the Mexican bean beetle, is a serious pest of beans including soybeans (Guyon & Knull 1925). The European alfalfa beetle, Subcoccinella vigintiquatuorpunctata (L.) was discovered in 1972 in Pennsylvania (Annonymous 1974). While an important pest of alfalfa and clover in Europe, it has been found feeding only on bouncing bet, Saponaria officinalis, campion, Lychnus alba, and oatgrass, Arrhenatherum elatius in the United States (Annonymous 1974).

Chilochorini (Chilochorinae) superficially resemble Epilachnini when senti are well-developed as in Chilochorus (fig. 34.571), or some Coccinellini when senti are more reduced. However, the presence of large pores of repugnatorial glands (fig. 34.587) on the abdomen will separate them easily from both. Chilochorini feed primarily on aphids and scales, therefore are used for biological control (Huffaker & Doutt 1965). For example, Exochomus flavipes Thungerg, indigenous to South Africa (Geyer 1947a, 1947b), was successfully used in the United States against mealybugs infesting commercial greenhouses (Doutt 1951). E. quadripustulatus (L.) was released against the wooly aphid Adelges piceae (Ratz). The twice-stabbed lady beetle, Chilochorus stigma (Say), is an important predator of the Florida red scale, Chrysomphalus aonidum (L.) which infests citrus groves (Muma 1955a, 1955b).

Coccinellini (Coccinellinae) are the best known coccinellid larvae because they live exposed, are very active, relatively large, and brightly coloured. The body armature is very diverse in this tribe (figs. 34.572, 34.579-34.581) and all structures are represented except scoli. These larvae can be distinguished from those of other tribes by the lyre-shaped epicranial suture of the head (fig. 34.583), the bidentate apex of the mandible (fig. 34.599), the reduced, inconspicuous third antennal segment (fig. 34.606) and the well-developed body armature. All native Coccinellini are beneficial and several foreign species have been introduced to aid in control of pests (DeBach 1964; Hodek 1967, 1973). Some species are widely distributed and well known. Anatis mali (Say), the eye-spotted lady beetle, bears senti on the body similar to fig. 34.580, and occurs on conifers where it is able to survive at low prey densities (Smith 1965; Watson 1976). The spotted ladybird, Coleomegilla maculata (De Geer) (fig. 34.621), eats pollen as well as aphids and is usually found on herbaceous plants, wild and cultivated, where its food is abundant (Smith 1965). Hippodamia species are important aphid predators (Cuthright 1924; Hodek 1973) and a common species, Hippodamia convergens Guerin, the convergent lady beetle (fig. 34.579), can keep aphids in check in alfalfa fields (Cooke 1963). Adalia bipunctata (L.) (fig. 34.581), the 2-spotted ladybird, is a widespread polymorphic species (Hodek 1973) which prefers trees above 2 m. Consequently, it is especially beneficial in orchards and groves where it is the most important coccinellid aphid predator (Smith 1958; Putman 1964; Hodek 1973). Coccinella species (fig. 34.572) are known as aphid predators (Palmer 1914; Clausen 1916; McMullen 1967), and some have become established after repeated releases over large areas; others like C. undecimpunctata L., are becoming well established on their own, along with the aid of man's commerce (Watson 1979; Wheeler & Hoebeke 1981).

Coccidulini (Coccidulinae) much resemble Coccinellini but differ by the features of the last abdominal segment (fig. 34.622) and antenna (fig. 34.602), their dull coloration, and the presence of a thin powdery coating of wax (Pope 1979). Their biology is not well known. Coccidula live in wet habitats. Rhyzobius ventralis (Erichson) has been introduced from Australia to California and Hawaii for control of scale insects (Pope 1981; Richards 1981).

Scymnini and Hyperaspini larvae are strikingly different from others because of their thick coating of wax (fig. 34.577) which is absent or inconspicuous in other tribes.

Scymnini (Scymninae) larvae have very sharp unidentate mandibles (fig. 34.594) and very small tubercles on the abdomen (fig. 34.573). Scymnus species feed mainly on aphids; some are useful predators in red pine plantations (Gagne & Martin 1968), cotton fields (Davidson 1921b) or sugarbeet fields (Buntin & Tamaki 1980); others attack psyllids and are beneficial in pear orchards (Westigard et al. 1968) while a few feed on mealybugs in citrus groves (Muma 1955a), or on phylloxera on wild grape (Wheeler & Jubb 1979).

Hyperaspini (Scymninae) larvae are separated from all others by the unique dome-shaped, 1-segmented labial palps (fig. 34.592). Hyperaspis (figs. 34.576, 34.577) species are known as efficient predators of scale insects (Simanton 1916; Boving 1917; Phillips 1963).

Noviini (Coccidulinae) is the only tribe where the larvae have only 2 pairs of sclerotized tubercles and 1 pair of soft lateral projections on the abdominal segments (fig. 34.574). Rodolia cardinalis Mulsant, the vedalia lady beetle, is a famous classic example of successful use of coccinellids in biological control of coccids (DeBach 1964).

Psylloborini (Coccinellinae) larvae are immediately recognized by the multidentate apex of their mandibles (fig. 34.595). They differ from other tribes in that they are mycophagous and feed on mildew. They are beneficial because they eat destructive fungi (Davidson 1921a).

Larvae of the 4 remaining tribes are usually overlooked because of their small size. Microweisea larvae (fig. 34.575) in the tribe Sticholotini (Sticholotinae) are easily identified by the 2 large flattened setae at the apex of the tibiae (fig. 34.618). They are beneficial scale feeders (Burgess & Collins 1912; Muma 1955a; Sharma & Martel 1972).

Serangiini (Sticholotinae) larvae have the body densely covered with fine setae (fig. 34.624) and their tibiae are unusually slender (fig. 34.590), characters which distinguish them from all others. Delphastus species in this tribe are predators of Aleyrodidae (Muma 1955a, 1955b).

Stethorini (Scymninae) larvae resemble superficially the Serangiini but are separated from them and all other tribes by the few large setae fixed on small tubercles covering the body (figs. 34.578, 34.623) and their short tibiae, apically truncated (fig. 34.588). They feed chiefly on mites, and many Stethorus species are active predators of these pests (Fleschner 1950; Robinson 1953; Putman 1955a, 1955b; Putman & Heme 1966; Tanigoshi & McMurtry 1977).

Scymnillini (Coccidulinae) larvae are distinguished by their unusual, large, antennae (fig. 34.600). Their biology is poorly known. Scymnillus aterrimus Horn has been reported as an incidental predator of scale insects in citrus groves (Muma 1955b).

Description: Coccinellid larvae are extremely diverse as described in the previous section, and illustrated in the family key, where they key out at several couplets. Therefore, they cannot be distinguished altogether by only 1 or 2 characters as in many beetle families. On the other hand, larvae of each tribe show a distinctive general habitus and have morphological features which are shared by all members of the tribe. The striking flattened larvae of the Palaearctic Platynaspini do not occur in North America.

Head: Hypognathous, usually rounded (fig. 34.582), sometimes elongate (fig. 34.585) as in Microweisea, or transverse as in Hyperaspini, Platynaspini, and some Scymnini (fig. 34.584). In most species, the head is completely sclerotized, but sometimes it may be partly or only very slightly sclerotized. The epicranial suture is usually distinct, V-shaped (fig. 34.585), Y-shaped (fig. 34.582), lyre-shaped (fig. 34.583), or absent (fig. 34.584) but the epicranial stem is usually absent. The antenna of the typical form of coccinellid larvae consists of 3 sclerotized segments (figs. 34.600, 34.602, 34.603), and bears a large spine-like seta on the membranous apical area of the second segment. However, they may appear to be 2-segmented (figs. 34.601, 34.605, 34.606) or even 1-seg-mented (fig. 34.604) when the third, and sometimes the second and third segments are reduced and not sclerotized; in those cases the homology of the segments apparently missing is often difficult to establish (Sasaji 1968b). The labrum is distinct and transverse (fig. 34.582).

The mandible is either apically simple and acute (figs. 34.593, 34.594), bidentate (figs. 34.596, 34.599), or multi-dentate in plant feeders (figs. 34.595, 34.597); the mola is usually present but reduced (figs. 34.595, 34.596 34.598, 34.599), highly reduced in Microweisea (fig. 34.593) and absent in Epilachna (fig. 34.597); a retinaculum may be either absent (figs. 34.593, 34.594), developed with 1 tooth (fig. 34.596), or multidenticulate (fig. 34.595). The maxillary palps are generally 3-segmented, but are 2-segmented in Noviini (fig. 34.609). The labial palps are either 1- or 2-segmented (figs. 34.591, 34.592). The labium has the submentum fused with the ligula (fig. 34.586).

Thorax and Abdomen: Pronotum with 2 or 4 plates. Meso- and metanotum each with 2 plates and distinct armature. Legs usually long and slender (figs. 34.589*64.590), short in Hyperaspini and Stethorini (fig. 34.588), consisting of 5 segments (coxa, trochanter, femur, tibia and claw-like tarsungulus). Tarsungulus curved (fig. 34.620), with a robust quadrangular tooth in some species (fig. 34.619). The apex of the tibiae usually bears clavate or flattened setae which are important in taxonomy (figs. 34,588, 34.617, 34.618).

Abdomen 10-segmented, widest basally, tapering to caudal end, dorsally with distinct armature, usually characteristic for each tribe. The tenth segment may be modified as a proleg or a sucking disk. Pores of repugnatorial glands may occur on each antero-lateral margin of terga in the coria between segments (fig. 34.587).

Spiracles: Small, annular, and located on abdominal segments 1-8 (fig. 34.587).

Comments: The larval stage of most coccinellid species consists of 4 instars. The first instar can be recognized by the paired egg-bursters on pronotum, and differences in proportions in size of head, abdomen, legs, setae, etc. Changes occur in coloration, proportions and armature of the body between successive instars. Larvae of the first and second instars are monochrome, with sclerotization and armature less developed than in older instars. Larvae of the third and fourth instars are usually brightly coloured and well sclerotized.

Palearctic coccinellid larvae are now fairly well known with the recent contributions of several authors (van Emden 1949; Savoiskaya 1957, 1960, 1962, 1964a, 1964b; Kamiya 1965; Sasaji 1968a, 1968b; Klausnitzer 1970; Savoiskaya & Klausnitzer 1973). The taxonomy of the Nearctic coccinellid larvae has not been comprehensively studied; only the early works of Boving (1917) and Gage (1920) provide a general treatment of the family. With the field key of Storch (1970) one can identify the larvae of 5 common native species. Phuoc and Stehr (1974) studied the morphology and the phylogenetic relationships of coccinellid pupae based on their morphology and suggested the need for a similar study of the larvae.