The Surinam Cockroach

With the immanent publication of the Guidebook to Australian Cockroaches, readers of this blog can expect an emphasis on cockroaches for a time. There are additional cockroach photos on the Flickr site noted in the left margin for those who might be interested.

The Surinam Cockroach (Pycnoscelus surinamensis (Linnaeus); Blaberidae; Pycnoscelinae) is one of some 12 known species in the genus. Two have been recorded from Australia: P. surinamensis and P. indica. The latter species has been collected on Norfolk Island along with the former but P. indicus has not been found on the Australian mainland.

In Australia P. surinamensis is known from several localities in New South Wales and Queensland. Despite its name, it is thought to have originated in the Indomalayan Region. Here in Kuranda it is common in compost heaps and in roof gutters where leaves accumulate. It does not seem to enter houses but is of economic concern because it damages plants, especially seedlings, by its feeding habits.

To 1998 it was known as the only obligatory parthenogenetic, thelytokous cockroach. What that means in plain English is that females can reproduce without mating. Males are rare and when the occur they are sexually non-functional.

From an economic standpoint, that means that a single nymph can give rise to an entire population of this cockroach. So the species can be spread easily. The cockroaches are moved about in nursery stock, soil, stock feed and the like. But even though this cockroach is tropical and subtropical its its habitat requirements, it can live quite nicely in greenhouses in temperate regions.

The Surinam Cockroach

Pycnoscelus surinamensis (Linnaeus)

The Surinam Cockroach is easily recognised by its black head and pronotum, the latter of which has a yellow margin near the head. It is a good flier and can be found at lights where it occurs.

Roth (1998) reported that P. surinamensis was derived from its relative P. indicus, a species that has males and is slightly smaller and instead of a black head, has a head with a black vertical stripe. It cannot reproduce parthenogenetically and does not readily, if at all, fly. They live in burrows and are apparently of no economic concern. The distribution of the species is similar to that of P. surinamensis.

Black Butcher-birds, Craticus quoyi, learn to find Surinam Cockroaches all they have to do is toss leaves out of roof gutters-- (but not thoroughly enough to be useful!). The cockroahces are large enough to be worth the effort and are a good source of fat and protein.

The Surninam Cockroach is almost a perfect lab animal. It reproduces readily in captivity and is easily cared for. It does not have a disagreeable odour and females look after their young. Children find them intriguing. 

Literature

Roth, L. M. 1998. The cockroach genus Pycnoscelus Scudder, with a description of Pycnoscelus femapterus, sp. nov. (Balttaria: Blaberidae; Pycnoscelinae). Oriental Insects 32: 93-130.

Australian Earwigs

Most gardeners in the temperate parts of Australia and in the northern hemisphere have a very negative image of earwigs. That is not unreasonable because the only one they see is the European Earwig, Forficula auricularia. This species feeds on flowers and vegetables at night rendering flowers useless and gardeners frustrated. European Earwigs are difficult to control because they really cannot be killed by spraying. They are "positively thigmotactic", like all earwigs. What this means is that they are "programmed" to spend most of their time in close quarters. So, during the day they can be found under rocks, in cracks in trees or, as with many Australian species, under bark. They, therefore, avoid the normal spraying control schemes.

Innovation is often the solution for earwig problems. A flock of bantam hens or Japanese Silkies can remove earwigs from a veggie patch-but they will also dine on the veggies. Some people crumple newspapers and the thigmotactic earwigs are drawn to the newspapers can be collected in the morning and the earwigs can be harvested.

But back to the Australian species. Even though we do have the European Earwig and one or two others that cause problems, we have some spectacular species. The world's largest and smallest earwigs can be found in Australia.

Earwigs are in the order Dermaptera. The Australian Faunal Directory has an important contribution to the knowledge of Australian earwigs. This has been compiled by Prof. G. Cassis and his colleague Dr Fabian Haas. A concise overview of earwig biology, ecology and the taxonomic knowledge of species is presented there.

Earwig biology can be complex. Females of some species look after the eggs and young. Males have pinchers that are larger than those of the females that are probably used in male combat. Although earwigs live in tight places, the chances of one entering a persons ear while sleeping at night, are very slight. But it can happen!

Briefly there are 85 described Australian species in seven families. It is estimated that three times that number probably exist on the continent. Australia is a hotspot for earwigs but generic endemism is low with only about 10% of the genera endemic to the continent.

 Echinosoma yorkense Dohrn; Pygidicranidae; Echinosomatinae

Aptly named, the genus literally means "spiny body". And when viewed up close, that's exactly what it looks like

  Echinosoma yorkense Dohrn; Pygidicranidae; Echinosomatinae

The spiny surface of the body of the Cape York Earwig.

 Apachys sp, probably queenslandicus; Apachyidae

A handsome large and very flat earwig that often flies to lights. Its rapid movments defy a good, close look but when tossed into the "dishwashing bin" the earwig is a bit befuddled for a few seconds and a good photograph is possible.

?Nala lividipes (Dufour) Labiduridae; Nalinae 

This earwig is a regular visitor to lights in the rainforest as well as at inland locales where eucalyptus and acacias are dominant.

 ?Nala lividipes (Dufour) Labiduridae; Nalinae 

Earwigs have an elaborate folding system for the large fan-like wings. Using their pinchers to aid in the folding process, the entire second pair of wings fit perfectly under the small first pair of wings (tegmina). The folding takes place in the "twinkling of an eye". 

 Cranopygia sp; Pygidicranidae; Pygidicraninae

This is large, spectacular species that infrequently comes to lights and when it does, it does not stay for long.

Elaunon bipartitus (Kirby); Forficulidae; Forficulinae

This earwig is often present in tremendous numbers and can be a pest. It can cover a light sheet and as dawn approaches, it can enter buildings and become a nuisance just due to its numbers. Like most earwigs it feeds on other insects. The pinchers can be used to hold the prey. 

Elaunon bipartitus (Kirby); Forficulidae; Forficulinae

This male has exaggerated pinchers that are probably used in male combat.

Summer Scarabs

Harbingers of summer. Every night during the year there is a scarab beetle of some sort at the lights but in the rainy season (summer) the most colourful ones appear. Even though I have reported on these before, it is nice to see them again.

 Anoplognathus sp

Christmas Beetles (members of the genus Anoplognathus) occur all over Australia in summer. They can be common at times and you can often see windrows of them in car parks or in brightly lit shopping centres. Most species are Anoplognathus.

 Anoplgnathus punctulatus-the most common species in the rainforest

 Anoplognathus smaragdina (rare blue morph)

I have reported on these beetles several times. Merely use the "Search" function and insert the genus name and you see them all.

                                                  Anoplognathus smaragdina (reddish morph)

 Anoploganthus aureus (Australian Gold Beetle)- a real gem

Calloodes grayianus (Gray's Christmas Beetle)

Larger than most Anoplognathus and seemingly less common

The Downside of the Rainy Season

After a lengthy period of dry weather (for Kuranda!) the rainy season has arrived and with it some nasties. I was looking through the sliding glass door and found this creature making its way across the glass. The rains have awakened the inactive leeches and this fellow/lass was in search of a meal.

 

The underside of the leech viewed from inside the room.

From the topside it appeared different from the usual leeches we see around the place.

It was not long before its colleagues had hit their mark. Now each trip to the light sheet in sandals or thongs results in and anticipant fellow traveller.