Saturday, 21 March 2009

DON'T BOGART THAT ROACH

EDITOR'S NOTE: It wasn't actually Maxy who came up with that title. I wonder if you can guess what it actually was?

This whole new species in the pet trade thing of mine is coming along nicely. I recently received an order, to be split between CFZ HQ and myself, consisting of 5 undiscribed species of cockroach. These are not cryptids, but they are the next best things; something science has yet to find a name for. They range from being tiny dark brown animals; right up to large showy species which are pretty enough for every naturalist to admire. In this little collection of gems, we have species that are known to species level, but appear to be a new sub-species, those known to genus, and 2 are known to family only. The last two especially are special indeed.

But before we take a look at the different species, let us first look at what the hell a cockroach is. They can be grouped into a couple of “looks”, each suited for a different habitat and mode of life (NOTE: these groupings are not taxologically correct). First we have the large bodied flightless species who spend their time either underground, or under shelter of some sort. We also have the smaller long legged reduced wing species, which lead a more active existence. They tend to run from danger, not fly. The small species with full wings are the most common; indeed, the British species belong to this group. Finally, you have the large winged species. Most of these are partially arboreal, but some become so large that they can no longer fly.


Termites, mantids and cockroaches are closely related, and the name Dictyoptera has been erected to name the group. Cockroaches first evolved in the early Carboniferous period, about 359MYA. Mantids evolved from “proto-cockroaches” about 145MYA in the very early cretaceous. So, as Tyrannosaurus rex was romping around biting chunks out of Ceratopsians, early mantids were munching their way through small invertebrates on a micro level. Proto-cockroaches (or Blattoptera) are cockroach like insects that the true cockroaches first evolved from. Looking at a large cockroaches’ leg, you can see the numerous large spines projecting downwards from the leg. It is not hard to see how these could have evolved into raptorial appendages. Termites are just social wood eating cockroaches. They probably evolved about 120MYA in the Cretaceous from a similar group to Cryptocercus, a small wood eating cockroach. Genetic studies have shown that Cryptocercus shares more DNA with termites than any other genus of cockroaches. It is the only cockroach to exhibit true social behaviors like caring for it’s young. I always find it funny when I say “cockroach” to people, and get a repulsed face. Say mantis or termite to them, and they usually hold them with regard and respect in their mind. You now know that they are basically the same thing.

Cockroaches are best known for being pest insects, which some of them are. But only 25-30 species out of the 4,000 around today are pests. They are generally tough animals, able to survive for a long time without food or water. Indeed, that old myth about cockroaches being able to survive for a month without it’s head is actually true!
In cockroaches, the head performs sensory functions like sight and smell, as well as being the holder of the mouth through which the roach drinks and feeds. Like all insects, the mouth is not used as a respiratory organ, instead they breathe through a series of tubes called trachea. Outlet holes called spiracles on the side of the abdomen open into the trachea, which, like our lungs, feed oxygen to the tissues, and remove carbon dioxide. Large species, with their high oxygen requirement, need to pump their abdomen often to keep air moving through the tubes. Insects also have no brain, they instead have ganglia decentralised throughout the body. Each ganglia controls, say, one pair of legs and acts both independently and in combined movements with the other pairs. In chordates, decapitation leads to death as almost all functions are controlled by the brain. In insects, they will carry on living until starvation, desiccation or predation claim them.

Another myth is that cockroaches will survive through a nuclear war. Well, they will certainly survive better than us, but for an insect, they are nothing special. Most cockroaches have a radiation resistance 6-12 times higher than a human, but animals like flies have even higher resistances. Radiation affects cells only when they are dividing, either by mitosis or meiosis. In humans, cells divide constantly to grow our bodies, repair ourselves or to produce sex cells. In insects, cell division only occurs at ecdysis (skin shedding). Only after they have shed their skin, do the cells begin to divide to quickly grow their bodies before they harden. If a nuclear blast occurred whilst they were hardening, they would be effected. If it occurred whilst the insect was hard, there would be little effect to the insect. However, long-term radiation could hit the insects when they shed, so they are as at risk as us to long-term radiation.

Cockroaches are generally silent animals, but supposedly there is a Floridian species which makes a chirping noise. Better known is the hiss that members of the tribe Gromphadorhini make by contacting their abdomen and forcing air out of the spiracles to create a predator repelling hiss. Members of this group (particularly from the genus Gromphadorhina) are common pets for those with a taste for the unusual, and are often seen in zoos as a handalable exhibit because they are a very large insect that although very impressive looking, is actually very calm when used to being handled. Cockroaches are in fact fairly large for insects. Like mantids, the smallest members of the group are about thumbnail sized (with the average being just above this size), whilst the group contains a very high number of large insects. Some of the largest and most impressive are:

Blaberus giganteus, the giant cave cockroach. At up to 90mm long, this is one of the longest cockroaches. Males are slim and fly well, but females have such massive bodies that the best they can manage is a sort of controlled fall. Males are often aggressive to each other, and both sexes release a very pungent smell which always reminds me of a nice vaguely fruity chemical. A few nymphs of this species usually retail for a couple of quid each.
Macropanesthia rhinoceros is the largest cockroach. At 75mm long, it is not the longest, but it’s sheer bulk more than makes up for this. They can weigh about 35g, which is huge for a terrestrial arthropod. They live for over 10 years and feed on eucalyptus bark and leaves exclusively. They dig and live in deep burrows with networks all around. Males (being larger and with a shovel shaped pronotum) do most of the digging, and the young usually stay in the burrow for a year before they move off. An adult pair of this species can set you back £80!
Megaloblatta insignis is the longest cockroach. At 105mm long, it is a huge beast that has been very poorly documented in the wild. It apparently (and very oddly) mimics larger Blaberus species, but differs in a few areas obvious to a layman, chiefly amongst which, no Blaberus is the uniform brown that M. insignis is. This could be something to do with the defensive chemical I spoke about earlier, but this is just my hypothesis and not scientific fact. This species has not been raised in captivity in the west.

But enough about roaches as a whole, we need to look at the species currently in my care. We start with a species known in the trade as the African Bullet Roach. Why? Well, they are from Africa and move as fast as a bullet! They are a small species getting to between 12-17mm as adults and were first collected in about 1997/8 at the base of Mt. Kilimanjaro in Tanzania. They are so easy to keep and breed that they are being used as feeder roaches for larger amphibians and reptiles. Just run that through your head, an unidentified species, being so common and numerous, that it is thrown to toads without a second glance!


The second species is one that I have yet to photograph properly, due to their small size and fast speed! This is Blaberidae sp. “Kenya”. Notice the “dae” on the end of that name. This means that this species is only known to family level, not even genus (like the above species). Males are an appealing orange colour, but females are a dark brown with reduced wings. They are only small at 10-12mm, but I am really looking forward to breeding them.

Now we look at Pycnoscelus sp. " Malaysia”, a small parthinogenic species (where females can produce offspring without a male) related to the sort-of-pest-sort-of-not Pycnoscelus surinamensis which causes a problem with its size and speed by being able to do well in most conditions (as long as there is a lot of moisture), so it jump’s animal tanks easily. They are tiny, which adults rarely reaching 10mm.


A cracking species is Eublaberus sp. “Pantanal”. This species is related to two common roaches in the hobby, E. disanti and E. posticus, but has much more black on it’s head with paler wings. It is found in a more southerly area than the other two species, and at 50mm, it is longer than the other two species. It is a stunning critter and both nymphs and adults are very showy whilst being rather shy and tending to burrow.



Finally, we have a new colour form of Eurycotis opaca, a large species up to 50mm long. It is related to pest species, but is itself not a pest. It has the build of a running species, but it is much larger than most. Adult’s have a blaze of colour on the pronotum which looks to me vaguely like a setting sun.

I have tried to contact a chap called Darren Mann, an expert in cockroaches, to see if he can identify whether it is worth naming them ourselves, or if they turn out to be a colour form of described species. He is out of office until early April, but naturally, I will keep you updated on developments.
We are also working on a project to try and document the behaviour and biology of these animals involving volunteers from the CFZ readershi[, so watch this space.

1 comment:

  1. I would just like to add, the species names for the photos are as follows:

    1. Ergaula capucina, adult male
    2. Lucihormetica subcincta, adult male
    3. Creobotra gemmatus, adult female
    4. Princisia vanwerebeki, sub-adult male
    5. Gromphadorhina oblongonata, adult female
    6. African bullet roach, adult male
    7. Pycnoscelus sp. "Malaysia", adult female
    8. Eublaberus sp. “Pantanal", sub-adult female
    9. Eublaberus sp. “Pantanal", adult female
    10. Eurycotis opaca, adult female

    ReplyDelete