Adephaga

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Adephaga
Temporal range:
Ma[1]
Cybister limbatus, a member of the family Dytiscidae (predaceous diving beetle)
Carabidae
(ground beetles)
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Coleoptera
Suborder: Adephaga
Schellenberg, 1806
Families
Image by Harold Maxwell-Lefroy - Adephaga

The Adephaga (from

predaceous diving beetles and whirligig beetles
.

Anatomy

Adephagans have simple

sternum is completely separated by the hind coxae
, which is one of the most easily recognizable traits of adephagans. Five segments are on each foot.

Wings

The transverse fold of the hind wing is near the wing tip. The median nervure ends at this fold, where it is joined by a cross nervure.

Internal organs

Adephagans have four

polytrophic
.

Chemical glands

All families of adephagan have paired

epidermal cells contiguous with the integument. The glands have no connection with the rectum and open on the eighth abdominal tergum
.

Secretions pass from the secretory lobes, which are aggregations of secretory cells, through a tube to a reservoir lined with muscles. This reservoir then narrows to a tube leading to an opening valve. The secretory lobes differ structurally from one taxon to another; it may be elongated or oval, branched basally or apically, or unbranched.

Delivery of glandular compounds

Secretion can occur in multiple manners:

  • Oozing: if the gland is not muscle-lined, the discharge is limited in amount.
  • Spraying: if the gland is muscle-lined, which is typically the case of carabids, the substances are ejected more or less forcefully.
  • Crepitation: boiling noxious chemical spray ejected with a popping sound. Crepitation is only associated with the Brachininae carabids and several related species. See bombardier beetle for a detailed description.

The secretions differ in the chemical constituents, according to the taxa.

Carabids typically produce carboxylic acids, particularly formic acid, methacrylic acid, and tiglic acid, but also aliphatic ketones, saturated esters, phenols, aromatic aldehydes, and quinones
.

Hygrobiidae also possess paired prothoracic glands secreting steroids
; and the Gyrinidae are unique in the extended shape of the external opening of the pygidial gland.

The function of many compounds remain unknown, yet several hypotheses have been advanced:

  • As
    predators; some compounds indirectly play this role by easing the penetration of the deterrent into the predator's integument
    .
  • Antimicrobial and antifungal agents (especially in Hydradephaga)
  • A means to increase wettability of the integument (especially in Hydradephaga)
  • Alarm pheromones (especially in Gyrinidae)
  • Propellant on water surfaces (especially in Gyrinidae)
  • Conditioning plant tissues associated with
    oviposition

Distribution and habitat

ant nests
.

Feeding

Most species are

ectoparasitoids of insects (brachinine and lebiine carabids) or of millipedes (peleciine
carabids).

Reproduction and larval stage

Some species are

carabids.

The larvae are active, with well-chitinized cuticle, often with elongated cerci and five-segmented legs, the foot-segment carrying two claws. Larvae have a fused labrum and no mandibular molae.

Phylogeny

Adephagans diverged from their sister group in the

haliplid-like forms. The familial and tribal diversification of the group spans the Mesozoic, with a few tribes radiating explosively during the Tertiary
.

The adephagans were formerly grouped into the Geadephaga with the two terrestrial families Carabidae and Trachypachidae and the Hydradephaga, for the aquatic families. However this is no longer used as the Hydradephaga are not a monophyletic group. Modern analysis has supported the clade Dytiscoidea instead, which includes many aquatic adephagans, notably excluding Gyrinidae.

Cicindelidae often being treated as a distinct family from Carabidae.[4][5][6]

Cladogram of the relationships of living adephagan families after Vasilikopoulos et al. 2021[5] and Baca et al. 2021:[7]

Adephaga
Gyrinoidea

Gyrinidae

Caraboidea

Trachypachidae

Cicindelidae

Carabidae

(Geadephaga)
Haliploidea

Haliplidae

Dytiscoidea

Noteridae

Hygrobiidae

Aspidytidae

Amphizoidae

Dytiscidae

See also

References

  • Balke, M.; Ribera, I.; Beutel, R.; Viloria, A.; Garcia, M.; Vogler, A.P. (2008). "Systematic placement of the recently discovered beetle family Meruidae (Coleoptera: Dytiscoidea) based on molecular data".
    S2CID 86012007
    .
  • "Adephaga". Integrated Taxonomic Information System.
  • Adephaga Tree of Life