Monday, 4 January 2016

New Year's Eve 2015- A Cockroach Bonanza!

Click on the images to see them in larger size
We spent part of New Year's Eve with hundreds of other people sitting on the sand at Clifton Beach, just north of Cairns, Queensland. It was a pleasant night with no rain and bearable humidity.

It took a while for the fireworks to get underway, and I decided to have a look at the strand vegetation, just above the the highest of the high tide mark.

To my delight I discovered a treasure trove of local cockroaches.
They were on a oddly named shrub called Sea Lettuce Tree, Scaevola taccada.
This is a widespread native coastal plant.
The fruits are eaten by a Silvereyes, Cassowaries and small mammals. As you will see below, the flowers are attractive to insects, and at night, especially cockroaches.
Here a the widespread small cockroach, Balta scripta Hebard,  is feeding on exudates from the buds and developing seeds of the Scaevola.

Balta scripta is a very widespread and common cockroach in northern Queensland. It has a very broad range of habitat preferences ranging from this coastal strand habitat to the much more arid inland mixed woodland an grassland sites. Wherever it is found, it is common.

The strand flora at Clifton Beach comprises a mixture of native and local plants. There is a small reserve where a creek empties into the ocean that may harbour reptiles of the more bitey kind.

A dominant plant beyond the Scaevola is Singapore Daisy, Sphagneticola trilobata, a central American native that, although very attractive, has gotten away with itself. It occurs in marginal habitats in northern Queensland and outcompetes native plants, literally overtaking them. It can occupy long stretches of rainforest edges. It propagates from nodes and is difficult to control.

The prolific flowers are loaded with pollen and that attracts insects.
Here we see one of the many undescribed species of Johnrehnia with Singapore Daisy pollen attached to its antennae.
Note the pollen!

Here we see two undescribed species of the diverse genus Johnrehnia on the leaves of Singapore Daisy.

 Normally nocturnal cockroaches wander about at night and feed on particulate matter on leaf surfaces. It is like a smorgasbord to them!

Above are two undescribed species of Johnrehnia searching for food, the top on a Singapore Daisy leaf, the other on Mangrove Lily, Crinum pedunculatum. This plant is a native but is cultivated and the ones at Clifton Beach have been planted. They provide a very acceptable habitats to a variety of insects.

Above Johnrehnia sp feeds on Singapore Daisy pollen. Note the nymphs (small cockroaches) which may be young of its species or some other cockroach.
Another undescribed species of Johnrehnia attracted to the pollen banquet.

 Present in smaller numbers was this slightly larger native cockroach, Carbrunneria barrinensis Roth. It was also found feeding on Singapore Daisy pollen.
This very flat cockroach, Megamareta phaneropyga (Chopard) spends the daylight hours in leaf axils of pandanus, which was present in the area. Developing Crinum leaves, as well,  also harbour this species during the day.
All of the above cockroaches are in the very large family Ectobiidae. Two representatives of another family, the Blaberidae, were found in the strand vegeation at Clifton Beach. The one above is a species of the large and widespread genus Calolampra. Males are fully winged and commonly fly to lights. Females are flightless and live in leaf litter.
The Surinam Cockroach, Pycnoscelus surinamensis (Linnaeus) is a widespread, introduced cockroach whose origins are a mystery despite its common name. It is parthenogenetic. That means that it is represented only by females. So it takes only one individual to start a colony. That is how it gets around so easily. It occurs in suitable habitats along the east coast from Queensland to New South Wales. It does not seem to enter houses but can be found in compost heaps, gutters and here in a natural habitat where there is plenty of cover, food and high humidity. This is one of several cockroaches that is "falsely" ovoviviparous. Females produce an ootheca, eggcase, from which the young emerge while it is carried around by their mother. The young cluster around the mother feeding on exudates that she produces. Eventually they go off on their own. This was the least common of the cockroaches encountered on New Year's Eve. It can easily be moved around in compost, pot plants and the like.
 Other orthopteroid insects similarly attracted to the strand flora are this Raspy Cricket, Hyalogryllacris sp. This is a last instar and is probably preparing to moult into an adult under the cover of darkness.
 This predatory katydid, Phisis jinae Rentz was described from Green Island, not far from Clifton Beach. It has been subsequently found along the coast in several localities and always in the strand  and mangrove flora. It too is a last instar and appears to be readying itself to moult into an adult.
The Northern Grass Pyrgomorph, Atractomorpha similis Bolivar, is very widespread in northern and eastern Australia. It prefers grassy habitats and is commonly found in the strand vegetation along beaches.
These small stinkbugs, Pentatomidae, are using the Scaevola leaves for a get together.
This crambid moth, Nacoleia glageropa, is a very common species and it is probably attracted to the the pollen and nectar of the flowering plants.
The "abundance of riches" brings along the vertebrate predators. This is a small Mourning Gecko, Lepidodactylus lugubris. A cockroach would be a very suitable New Year's feast.
A larger Mourning Gecko lying in wait for a meal.

It should be stressed that all of the above cockroaches, with the possible exception of the Pycnoscelus, are native species and would not find your pantry suitable for survival. On the other hand, they live mostly in leaf litter, in large numbers, and they are probably very important in the breakdown of this material and its return to soil. Because their numbers are so high, they are most likely important food sources for vertebrates such as birds, lizards and frogs as well as other insects. So they should be encouraged. They are probably important pollinators of native plants as well.

The take home message here is that these insects are important members of our biota. Prescribed burning of their habitat will result in their loss for many years and eliminate the roles that they fulfil. 


Scott Ritchie said...

Nice way to start the year!

Scott R

Gary Wilson said...

Good stuff