Overview
(Greek, blatta = an insect that shuns light)
Blaberoidea, Blattoidea, & Polyphagoidea Superfamilies
Cockroaches are primitive orthopteroids and among extant orders have been grouped with Mantodea, Isoptera, Grylloblattodea, Orthoptera, Phasmatodea, Dermaptera, Embioptera, Plecoptera and Zoraptera, all groups which retain primitive features of the Neoptera (Brown 1982). McKittrick (1965) and others believe they are most closely related to termites. Although the Blattodea is presently relatively small, containing fewer than 4000 named species and about 460 genera, during the late Paleozoic era (Carboniferous), it was one of the largest of insect orders in numbers of individuals.
There is considerable variation in the size of Blattodea, not only between species, but intraspecifically as well. In Australia the smallest and most fragile species belong to
Nocticola
which are about 3 mm long and weakly sclerotised. The largest species belong to the Blaberidae, particularly the Panesthiinae. The wingless
Macropanesthia
rhinoceros
may attain a length of 65 mm and weigh about 20 grams (Day 1950) probably making it the bulkiest cockroach known.
There are thousands of species of cockroaches worldwide, but only about ten are household pests. All species have a flattened body with the head attached and constructed in such a way that the mandibles open vertically downwards. The compound eyes are generally well developed, but they may be absent in cave dwelling species. Simple eyes (ocelli) if present are represented by two pale spots. Cockroaches have filiform antennae (composed of short, straight segments) and the legs are often spiny. Body colour is generally reddish-brown, brown or black. Wings may or may not be present - many Australian native species of cockroach are wingless. When present, the forewings are often partially hardened into protective covers (tegmina) to prevent damage to the hind wings which are used for flying.
There is no metamorphic cycle of egg-larva-pupa-adult in these insects. The juveniles emerge from the eggs as wingless replicas of the adults (nymphs) and grow by successive moults until they reach mature size.
Cockroaches are essentially scavengers. The "domestic" species have been known to consume white-wash, books, boots, hair, skin, finger nails, ink, their own egg cases and any material that has food value. The Australian wood cockroaches eat plant debris while other species consume wood by employing flagellate protozoans to digest the cellulose in the same manner as termites.
To human economics, harm from cockroaches is not so much created by the amount of food consumed by the insects, but rather by the spoilage created through their activities. Faeces are left on any area where they have been feeding and their habit of first softening their meal by covering it with both digestive tract enzymes and stomach contents leaves extremely unpleasant odours behind. They are also well known as disease carriers. Australian wood cockroaches appear to be important in the food chains of arachnids such as spiders. Empty husks of numbers of cockroaches are sometimes found in the web/nest areas of spiders.
The biology of cockroaches has been reviewed by Cornwell (1968), Guthrie and Tindall (1968), Beier (1974) and Bell and Adiyodi (1981). Schal et al. (1984) summarised the behavioural ecology of cockroaches and Roth and Willis (1957, 1960) reviewed their medical and veterinary importance, and biotic associations. Princis (1962-1971) compiled the biological and taxonomic literature.
Termitoidea Superfamily
The Termitoidea occur mainly in tropical and subtropical regions. It contains over 2300 species, of which 258 described and at least 90 undescribed species occur in Australia.
They are soft-bodied insects with cryptic habits, living in family groups (colonies). Each colony contains several castes, morphologically and behaviourally specialised to perform different tasks. Three principal castes are recognised. (1) Reproductives. Primary kings and queens are fully sclerotised individuals derived from winged adults (alates), their wing remnants in the form of four small, triangular scales. Supplementary (or replacement) reproductives (neotenics) are usually less heavily sclerotised and either lack wing elements, or have rounded wing buds. (2) Soldiers. Sterile males or females and usually apterous, soldiers have heavily sclerotised heads armed with either large mandibles or a long snout (rostrum or nasus) from which threads of sticky secretion are fired. (3) Workers. Generally unpigmented and only lightly sclerotised, these apterous, sterile males or females lack special external modifications.
Immature stages of all these castes may also be present: wing-budded nymphs (reproductive nymphs), potentially fertile; presoldiers (white soldiers); and apterous larvae with small thoraces. Intercastes are also found occasionally.
The alates vary in length from 6--7 mm (small
Amitermes
and
Microcerotermes
) to 17--18 mm (
Mastotermes
) and in wing-span from 12 mm (small
Amitermes
) to 50 mm (
Mastotermes
). The soldiers and workers vary in body length from 2.5 mm (small
Tumulitermes
) to 15 mm (
Porotermes
and
Neotermes
).
World literature on termites has been abstracted by Snyder (1956--68), Ernst and Araujo (1986) and, from 1979--88, in
Termite Abstracts
. Snyder (1949) catalogued the world fauna. Major synoptic works include Krishna and Weesner (1969, 1970), Harris (1971) and Grasse (1982--86). Lee and Wood (1971) dealt with termites and soils. Several texts include useful documentation of particular aspects of termite biology: Keast et al. (1959) (Australian zoogeography and ecology); Brian (1978) (food and feeding, nutrient dynamics, role in ecosystems); Hermann (1979, 1981, 1982) (inquilines, defensive mechanisms); Watson et al. (1985) (caste differentiation); and Vinson (1986) (economics and control).
Hill (1942) monographed the Australian termites. Ratcliffe et al. (1952) gave a general account of them, as did Hadlington (1987). Perry et al. (1985a) provided a guide to south-western Australian termites, and Watson (1988) to termites in the Canberra region and south-eastern N.S.W.
Description
Blaberoidea, Blattoidea, & Polyphagoidea Superfamilies
Exopterygote Neoptera; bodies flattened dorsoventrally; head in repose with chewing mouth-parts directed downwards. Fore wings, when present, usually modified into hardened tegmina which are sometimes abbreviated or absent; hind wings, if developed, membranous; but these too may be reduced or absent. Legs cursorial, sometimes fossorial; tarsi 5-segmented. Male genitalia asymmetrical, female ovipositor concealed. Cerci with 1 to many segments. Specialised stridulatory organs rarely present. Eggs usually contained in an ootheca which may be carried externally until hatching or deposited on a substrate (oviparity), or retracted into a uterus or brood sac until parturition (ovoviviparity and viviparity).
Termitoidea Superfamily
Polymorphic, mandibulate, exopterygote Neoptera, living in social family units composed of a limited number of reproductive forms associated with their offspring, numerous wingless sterile soldiers and workers. Antennae moniliform; wings elongate, membranous, held flat over the body at rest, and capable of being shed by means of basal sutures; cerci short; external genitalia rudimentary or wanting.
Distribution
Blaberoidea, Blattoidea, & Polyphagoidea Superfamilies
The largest families worldwide are the Blattellidae and Blaberidae, and this also is true of the Australian fauna. Cosmopolitan species aside, many of the Australian taxa are endemic; notable among these are most Blattidae, most epilamprine and panesthiine Blaberidae, and many Blattellidae. Of the Australian Blattidae,
Methana
is found in the Oriental region,
Polyzosteria
occurs in the Oriental region, New Zealand and New Caledonia,
Tryonicus
is in New Caledonia, and
Celotoblatta
(=
Austrostylopyga
) is in New Zealand. All other recorded blattids seem to be confined to Australia where they are particularly abundant in the southern, central and western parts of the continent. The blattellid
Shawella
couloniana
was introduced from Australia into New Zealand where it has become established (Johns 1966). A few blattellids from Queensland are also found in New Guinea (Roth unpubl.). The monotypic family Cryptocercidae is confined to North America and eastern Asia.
Termitoidea Superfamily
The Australian termite fauna includes one endemic family, the Mastotermitidae, but in other families except the Termitidae the level of generic endemism is low. The 41 genera comprise 25 termitids, 8 kalotermitids, 5 rhinotermitids, 2 termopsids and
Mastotermes
. The termitid genera belong overwhelmingly to 1 of 3 highly endemic groups. Two are structurally specialised: the
Termes
complex, with soldiers having elongate, variously asymmetrical snapping mandibles (13 genera, 11 not known outside Australia) (Miller in press), and the Nasutitermitinae, with nasute soldiers (6 genera, 5 endemic). The third group, the
Amitermes
complex, includes
Amitermes
, our largest genus, with perhaps 100 species (80 included in the tally below). The other four genera are endemic, apparently derived from
Amitermes
.
Invasitermes
lacks soldiers, only the second termitine genus known to do so (Miller 1984a), but it appears we may have a significant, unrecognised fauna of small, soldierless,
Amitermes
-like species.
At least three exotic species, all
Cryptotermes
, have become established in Australia. On the other hand, several Australian species have been spread to other countries, apparently in poles and sawn timber:
Mastotermes
to New Guinea, and others to New Zealand (Bain and Jenkin 1983).
The most distinctive feature of the fauna is the presence of relict primitive genera in the Mastotermitidae and Termopsidae.
Mastotermes darwiniensis
, in some ways the most primitive living termite, is the only surviving member of a family that is represented in other continents by fossil species from Tertiary deposits. The two termopsid genera survive from Gondwana.
Stolotermes
, with three mainland species and one in Tasmania, is represented elsewhere by species in New Zealand and one in South Africa, and
Porotermes
has one species in south-eastern Australia, one in Chile, and one in South Africa (Calaby and Gay in Keast et al. 1959). Notable absences from the fauna are the Hodotermitidae (to which the endemic termitine harvesters
Drepanotermes
show many convergent similarities) and fungus-growing termites (Macrotermitinae), of major economic importance in Africa and Asia.
Two aspects of termite distribution within Australia are of special interest. The first is the paucity of species in rainforest areas. This is in marked contrast to the extremely rich termite faunas of other tropical rainforests, such as the Congo and Guyana. The second feature is the absence of some species of termites from certain types of soil. The black earths of inland north-eastern Australia are almost devoid of termites, although adjacent sandy-desert steppe soils have an abundant fauna. It is thought that the physical characteristics of the heavy soils, which crack deeply and widely in dry conditions and become waterlogged after rain, do not favour termite survival.
Mastotermes darwiniensis
, which is widely distributed across tropical Australia, is absent from rainforest and soils which once carried rainforest (Ratcliffe et al. 1952), nor does it occur on the extensive bauxite soils of Cape York Peninsula.