Tryonicus Mcker

Dead wood is a tremendously diverse resource that varies with plant taxon, size (branch to bole), location (forest floor to suspended in canopy),degree and type of rot, orientation (standing versus prone), presence of other invertebrates, and other factors. Cockroach species from

Table 3.2. Examples of cockroaches other than Cryptocercidae and Panesthiinae that have been collected from rotted wood.

Cockroach species

Habitat

Reference

Anamesia douglasi

Under bark, in rotting wood, in fallen timber

Roach and Rentz (1998)

Austropolyphaga queenslandicus

Colonies in preformed chambers in dead logs and stumps

Roach and Rentz (1998)

Lauraesilpha mearetoi

In soft wood of small, dead branches

Grandcolas (1997c)

Lamproblatta albipalpus

Rotten logs and banana

Hebard (1920a)

trucks, leaf litter

Gautier and Deleporte (1986)

Laxta granicollis

Under bark, in rotting

Roach and Rentz (1998)

Lax.tillyardi

wood

Litopeltis bispinosa

Rotting banana and coconut palms

Roth and Willis (1960)

Methana parva

Under bark, in rotting wood

Roach and Rentz (1998)

Panchlora nivea

Rotting banana and

Roth and Willis (1960)

coconut palms, rotten

Sein (1923)

wood

Panchlora spp.

Rotting logs, stumps,

Wolcott (1950)

woody vegetation

Fisk (1983)

Paramuzoa alsopi

Juveniles in dead wood

Grandcolas (1993b)

Parasphaeria boleiriana

In soft, rotten wood

Pellens et al.(2002)

Polyphagoides cantrelli

In rotting wood

Roach and Rentz (1998)

Robshelfordia hartmani

In rotting wood, females also collected in caves

Roach and Rentz (1998)

Sundablatta pulcherrima1

Abundant in decayed wood

Shelford (1906c)

Ylangella truncata

Adults under bark;

C. Rivault (pers. comm. to

juveniles deep in rotten

CAN)

tree trunks

1 Described as Pseudophyllodromia pulcherrima by Shelford (1906c); LMR's notes on the Shelford manuscript indicate it is in the genus Sundablatta.

1 Described as Pseudophyllodromia pulcherrima by Shelford (1906c); LMR's notes on the Shelford manuscript indicate it is in the genus Sundablatta.

most families have been collected from rotting logs (Table 3.2), but in the majority of cases it is unknown whether these feed on wood and associated microbes, if they depart to forage elsewhere, or both. This category is more fluid than generally recognized, and divisions in the dietary continuum of rotted leaf litter, soft rotted wood, and wood-feeding are not always easy to make. This is particularly true of the many cockroaches that bore into the well-rotted trunks and stalks of coconut and banana palms, which have been described as "gigantic vegetables with a stalk only a little tougher than celery" (Perry, 1986). Some cockroaches (e.g., Blaberus) are found in rotting logs as well as a variety of other habitats, others are not recorded anywhere else. Tryonicus monteithi, Try. macker-rasae, and Try. parvus are found in rotting wood and un der stones and pieces of wood in Australian rainforest, but never under bark or above ground (Roach and Rentz, 1998). Anamesia douglasi is found under bark and in rotting wood, but has also been observed on sand ridges (Roach and Rentz, 1998), perhaps sunning themselves like some other Polyzosteriinae. Groups of similar-sized juveniles of Ylangella truncata, probably hatched from a single ootheca, live in galleries deep in the interior of large rotting tree trunks. Adults are excellent fliers and are found most often just under the bark of these logs. Attempts to rear nymphs in the laboratory on pieces of rotted wood and a variety of other foodstuffs, however, were not successful (C. Rivault, pers. comm. to CAN).A species of large, reddish, heavy-bodied hissing cockroach has been observed in groups of 40 or 50 inside of rotten stumps and logs in riverine areas of southeastern Madagascar. Groups included both adults and nymphs (G. Alpert, pers. comm. to LMR). The least known cockroaches in this category are those with the elongated, cylindrical body form of many boring beetles. These include Compsagis lesnei (Chopard, 1952), found inside of tree branches (Fig. 1.14), and several species of Colap-teroblatta (= Poroblatta) (Roth, 1998a), which Gurney (1937) described as boring into stumps and logs in a manner similar to Cryptocercus. There are probably many more wood-boring cockroaches yet to be discovered, particularly in the substantial amount of dead and dying wood suspended in tropical canopies.

Both sexes of all species in the monogeneric family Cryptocercidae are wingless and spend their lives in decaying wood on the floor of montane forests in the Palearctic and Nearctic (Nalepa and Bandi, 1999). As might be expected for insects feeding on dead wood, their distribution and abundance varies in relation to patterns of tree mortality if other habitat requirements are met (Nalepa et al., 2002). Presently C. punctulatus in eastern North America is numerous at high elevations in logs of Fraser fir (Abies fraseri) killed by balsam wooly adelgid (Adelges piceae). Formerly they were easily found in chestnut logs (Castanea dentata) abundant on forest floors because of chestnut blight (Hebard, 1945). Occasionally, all families in a log are of the same developmental stage, suggesting that a particular log became suitable for colonizing at a particular point in time. A log may harbor only male-female pairs, for example, or only families with second-year nymphs (CAN, pers. obs.). Both Palearctic and Nearctic species of Cryptocercus occur in a wide variety of angiosperms and conifers, with the log host range determined by the plant composition of the inhabited forest. Well-rotted logs as well as those that are relatively sound serve as hosts (Cleveland et al., 1934; Nalepa and Bandi, 1999; Nalepa, 2003). The cockroaches are only rarely collected from wood undergoing the white rot type of decay (Mamaev, 1973; Nalepa, 2003); the conditions associated with white rot generally do not favor many groups of animals (Wallwork, 1976). Inhabited logs can be quite variable in size. Logs harboring C. primarius ranged from 10 cm to more than 1 m in diameter (Nalepa et al., 2001b). Cryptocercus clevelandi is most often collected in logs of Douglas fir, the large size of which buffers the insects from the warm, dry summers characteristic of southwest Oregon (Nalepa et al., 1997). Large logs provide insulation from winter cold, but C. punctulatus is also physiologically equipped to withstand freezing weather (Hamilton et al., 1985).

Wood-feeding cockroaches in the blaberid subfamily Panesthiinae are distributed principally in the Indo-

Malayan and Australian regions, with a few species extending into the Palearctic. Six genera live in and feed on rotting wood, and exhibit little variation in morphology and habits. Body size, however, can be quite variable; Panesthia spp. range from 15 to more than 50 mm in length (Roth, 1977,1979b, 1979c, 1982b). The best studied is Panesthia cribrata in Australia, found inside of decaying logs but also under sound logs, where they feed on the wood surface in contact with the ground. They are sometimes found in the bases of dead standing trees (Rugg and Rose, 1984a; Rugg, 1987). Host choice in these blaberids is similar to that of Cryptocercus. Panesthia cribrata in Australia (Rugg, 1987), as well as species of Panesthia and Salganea in Japan (K. Maekawa, pers. comm. to CAN) utilize softwood as well as hardwood logs. They generally use what is available, and when populations are high, they are found in a greater variety of log types (D. Rugg, pers. comm. to CAN).

All Cryptocercidae and wood-feeding Panesthiinae studied to date are slow-growing, long-lived cockroaches. Development takes about 4 yr in Cryptocercus kyebangen-sis (Park et al., 2002), C. clevelandi takes 5-7 yr, and C. punctulatus requires 4-5 yr. In the latter two species, adults pair up during the year they mature, but do not reproduce until the following summer. Thus the time from hatch to hatch in C. clevelandi is 6-8 yr, and in C. punctulatus 5-6 yr. Post reproduction, adults of these two species live for 3 or so yr in the field, females longer than males (Nalepa et al., 1997). Rugg and Rose (1990) calculated that the nymphal period of Pane. cribrata was at least 4-6 yr, and that the field longevity of adults exceeds 4 yr. Panesthia cribrata, as well as Pane. australis, Pane. matthewsi, Pane. sloanei, and Pane. angustipennis spadica live in aggregations, most often comprised of a number of adult females, an adult male, and nymphs of various sizes. Nymphs are also commonly found in groups without adults (Rugg and Rose, 1984a). Panesthia cribrata reproduces once per year, but probably gives birth each year (Rugg and Rose, 1989). All species of Cryptocercus studied to date live in monogamous family groups, and produce just one set of offspring, with an extensive period of parental care following (Seelinger and Seelinger, 1983; Nalepa, 1984; Nalepa et al., 2001b; Park et al., 2002). The panesthiine genus Salganea is also subsocial (Matsumoto, 1987; Maekawa et al., 1999b),but at least one species (Sal. matsumotoi) is iteroparous (Maekawa et al., 2005).

In Soil

Those cockroaches known to tunnel in uncompacted media such as leaf litter or loose soil occasionally make forays into more solid substrates. Periplaneta americana nymphs and adults have been observed digging resting sites in the clay wall of a terrarium (Deleporte, 1985), and Pyc. surinamensis can excavate tunnels that extend up to 13 cm beneath the soil surface. These tubes may end in a small chamber where juveniles molt and females bear young (Roesner, 1940). At least two unstudied blaberids in the subfamily Perisphaeriinae appear to live in permanent soil burrows. Female Cyrtotria (= Stenopilema) are found in a burrows surrounded by juveniles (Shelford, 1912b). Similarly, a female Pilema thoracica accompanied by several nymphs was taken from the bottom of a neat round hole about 15 cm in depth; there were about a dozen such holes in half an acre and all contained families of this species (Shelford, 1908). Cockroaches of a Gromphadorhina sp. have been observed in a ground burrow in grassland of the Isalo National Park in Madagascar. The heads and antennae of both adults and nymphs were projecting from the entrance, which was about 5 cm in diameter (G. Alpert, pers. comm. to LMR).

All other cockroaches that form permanent burrows in compacted soil belong to four Australian genera of the subfamily Panesthiinae: Macropanesthia, Geoscapheus, Neogeoscapheus, and Parapanesthia (Roth, 1991a). They are distributed mainly east of the Great Dividing Range with a concentration in southeast Queensland (Roach and Rentz, 1998). The giant burrowing cockroach M. rhinoceros is the best studied (Rugg and Rose, 1991; Mat-sumoto, 1992), but the biology of the other species is similar (D. Rugg, pers. comm. to CAN). All feed on dry plant litter that they drag down into their burrows. Burrow entrances have the characteristic shape of a flattened semicircle, but may be slightly collapsed or covered by debris during the dry season. Tunnels initially snake along just beneath the soil, then spiral as they descend and widen out; they tend to get narrow again at the bottom. Litter provisions are typically stored in the wider part, and the cockroaches retreat to the narrow blind terminus when alarmed. They are not known to clean galleries; consequently, debris and excrement accumulate (Rugg and Rose, 1991; D. Rugg, pers. comm. to CAN). Species distribution is better correlated with soil type than with vegetation type. Burrows of M. rhinoceros may be found in Eucalyptus woodland, rainforest, or dry Acacia scrub, as long as the soil is sandy. Other species are associated with gray sandy loams, red loam, or hard red soil (Roach and Rentz, 1998). The depth of Macropanesthia saxicola burrows is limited by the hard heavy loam of their habitat, and those of M. mackerrasae tend to be shallow and non-spiraling because they run up against large slabs of rock. The deepest burrows are those of females with nymphs, the shallowest are those of single nymphs (Rugg and Rose, 1991; Roach and Rentz, 1998). Female M. rhinoceros reproduce once per year, and nymphs remain in the tunnel with females for 5 or 6 mon before they disperse, initiate their own burrows, and begin foraging. These mid-size nymphs then enlarge their burrows until adulthood. Development requires a minimum of 2 or 3 yr in the field, but growth rates are highly variable. Adults live an additional 6+ yr (Rugg and Rose, 1991; Matsumoto, 1992). Males are occasionally found in the family during early stages of the nesting cycle. Both sexes emerge from burrows after a rainfall, with females foraging and males looking for females. Surface activity in M. rhinoceros occurs from just before midnight to a couple of hours after sunrise; peak of activity is 2 or 3 hr before sunrise. Small nymphs are never observed above ground (Rugg and Rose, 1991).

Recent evidence indicates that among the Panesthi-inae, the ecological and evolutionary boundaries between the soil-burrowing-litter-feeding habit, and one of living in and feeding on wood, are more fluid than expected. In 1984, Rugg and Rose (1984c) proposed that the soil-burrowing cockroaches be elevated to the rank of subfamily (Geoscapheinae) on the basis of their unique reproductive biology. Recently, however, a molecular analysis of three genes from representatives of nine of the 10 Panes-thiinae and Geoscapheini genera by Maekawa et al. (2003) indicates that these taxa form a well-supported monophyletic group, with the former paraphyletic with respect to the latter (Fig. 2.13). These authors propose that the ancestors of soil-burrowing cockroaches were wood feeders driven underground during the Miocene and Pliocene, when dry surface conditions forced them to seek humid environments and alternative sources of food. This suggestion is eminently reasonable, as there are isolated cases of otherwise wood-feeding cockroach taxa collected from soil burrows or observed feeding on leaf litter. Ancaudellia rennellensis in the Solomon Islands lives in underground burrows (Roth, 1982b), even though the remaining species in the genus are wood feeders. There is also a record of a male, a female, and 19 nymphs of Panesthia missimensis in Papua New Guinea collected 0.75 m deep in clay, although others in the species were collected in rotten logs (Roth, 1982b). Although the preferred habitat of the endangered Panesthia lata is decaying logs, Harley Rose (University of Sydney) has also found them under rocks, sustaining themselves on Poa grass and Cyperus leaves (Adams, 2004). Even individuals or small groups of C. punctulatus are sometimes found in a small pocket of soil under a log, directly beneath a gallery opening (Nalepa, 2005), particularly when logs become dry. These examples are evidence that the morphological adaptations for burrowing in wood also allow for tunneling in soil, and that the digestive physiology of wood-feeding Panesthiinae may be flexible enough to al low them to expand their dietary repertoire to other forms of plant litter when required.

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