Nature's Chemical Warfare
Experiences
of rearing Alloeophasma cyllarus (PSG 220)
(An article that I wrote for the PSG newsletter)
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Nature's Chemical Warfare Experiences
of rearing Alloeophasma cyllarus (PSG 220) (An article that I wrote for the PSG newsletter) |
|
I
initially encountered Alloeophasma cyllarus and Anisomorpha ferruginea
at my first ever PSG meeting, in July last year.
I didn’t know anything of these rather inconspicuous-looking species
prior to the Livestock Distribution, and so did not instantly raise my hand when
Ian picked up the box ready to give them away.
However, I was very intrigued by the general response when Ian referred
to them – with a tone of caution - as “sprayers”.
Most people shook their heads in decline, and I was left wondering what
could be so bad about these rather anonymous-looking phasmids!
Thus, rather foolishly perhaps, I raised my hand, and left at the end of
the day with a tub of one and two tubs of the other.
I
have been rearing these species for almost a year now, and for some reason have
actually become rather fond of “sprayers”.
In this short article I shall attempt to provide an introduction to these
phasmids, and describe to you their rather effective chemical defence mechanism.
Alloeophasma
cyllarus and
Anisomorpha ferruginea are two species of the sub-family Pseudophasmatinae.
They are similar in size, adult females being approximately 50-60 mm in
body length, and adult males approximately 35-40 mm.
A. cyllarus comes from Jamaica, whereas A. ferruginea is
native to Southern USA.
All stages and both sexes of this species are a dull
mottled brown colour. The texture
of the body appears to be quite matt and almost ‘feathery’, which would aid
the insect to blend in against a background of dead leaves and bark.
The
adults of both sexes are visually similar, the only real difference being that
males are a lot smaller and, as with many species of phasmids, they have a
characteristic bump on the underside of the abdomen (known as the subgenital
plate). Adults of this species
have small, almost convex forewings, which are somewhat reminiscent of pointy
shoulder pads! The hindwings, which
reach down to the last abdominal segment when folded, are the same colour on the
surface (the pre-anal segment) as the forewings, whilst the rest of the
hindwing is seen to be translucent and almost colourless when outstretched.
When
viewed from above, a thin black stripe is visible, which runs from between the
eyes down to between the forewings. The
long antennae of this species appear attractively stripy, being composed of
alternating straw-coloured and dark brown-coloured segments.
The
ova are approximately 3mm in length, and are a dull ash-grey colour when dry.
The operculum (lid) is barely visible, and the ovum as a whole could be
described as being almost cylindrical in shape, with slightly rounded ends and
being slightly swollen in the middle. Whilst
writing this paragraph I accidentally crushed an ovum (sorry!) and noted, to my
surprise, that the liquid contained within was deeply magenta-coloured.
As
with most phasmids, I keep the ova on a layer of vermiculite contained within a
mesh-lidded plastic tub. I lightly
spray the ova every few days, and I find that the nymphs hatch out after
approximately 3-4 months.
Both
sexes of Anisomorpha ferruginea are apterous (i.e. without wings).
In contrast with Alloeophasma cyllarus, the body of this species
is relatively glossy. Viewed from
above, it would appear that the sausage-shaped body of the adults is
predominantly dark brown, with two paler brown stripes running longitudinally
down the length of the dorsal (i.e. upper) surface.
As with Alloeophasma cyllarus, the main factor distinguishing
males from females is their smaller size. In
addition, the aforementioned pale brown stripes are generally thinner in the
males, making their body appear to be a darker colour overall.
The ova of this species are approximately 2-3 mm in
length, and chocolate-brown in colour. Their
shape is cylindrical though imperfect, and with irregular edges running down the
length. Nymphs of this species
generally hatch out within 3 months.
I
keep both species in small, partially ventilated plastic tanks.
I spray them rarely, since Pseudophasmatinae apparently prefer
less humid conditions, and I feed them only on privet (Ligustrum vulgare)
although I have read that lilac (Syringa spp.) is also accepted.
Alloeophasma
cyllarus and
Anisomorpha ferruginea display similar defensive behaviour, much of which
is characteristic of many members of the Pseudophasmatinae.
Firstly, these species are notably crepuscular in nature (i.e. active in
the twilight). This is typical of most phasmid species since is serves to
protect them from daytime predators (for example, birds).
However, the aforementioned two species go one step further, in that they
actively search out dark crevices in which to hide, such as the underside of
rocks and bark, and in the corners of their tank.
If space is lacking, the insects will not hesitate to pile on top of one
another, in order that they are all able to hide away in the dark.
I have found that it helps to place a rolled up tube of corrugated
cardboard, or something similar, in their tank.
The insects like to hide in this during the daytime, and when I need to
clean them out, I simply lift out the tube and all the insects come with it!
A
second defence mechanism of this species is that they run fairly fast, and do
not stop moving until they have found someplace secure in which to hide.
However,
the most notable defence tactic is that, when threatened, they are capable of
spraying a fine mist of a very offensive chemical. In both species this appears to originate on the pronotum,
just below the head. You can
actually see the spray when a light is shining behind the insects; using this
set-up, I have seen Alloeophasma cyllarus emit a fountain 10cm high!
Because
of this chemical defence mechanism, I’d suggest that “sprayers” be handled
minimally, and should not be kept by children, nor by people prone to breathing
difficulties or allergies.
The
vapour emitted by Anisomorpha ferruginea smells a little like blue
cheese, whereas that of Alloeophasma cyllarus smells somewhat peppery.
Both contain a component that irritates the throat and nasal passage,
causing one to cough and sneeze quite dramatically!
If the chemicals enter a small wound, such as those inevitably caused by
collecting bramble for one’s phasmid collection, a stinging sensation is
experienced, and the area can become red and enflamed. What’s more, the spray
of a related species, Anisomorpha buprestoides1, has been
observed to cause temporary blindness to man, though I personally have not had
the misfortune of being sprayed in the eyes by any of the Pseudophasmatinae!
Okay,
I realise that I have not painted too pleasant a picture of these two species,
practically likening them to skunks or walking puffballs!
Yet, as I said before, I personally am quite fond of these
“sprayers”. Is it simply an
attraction to the more sinister side of nature, in the same way that some people
are enthralled by Black Widow spiders, dangerous snakes and the like??! Or is it
merely that I pity these very attractive insects, who are only behaving in a way
that has enabled the species to survive amid the numerous predators that exist
in their natural environment? Whatever the reason, I assure you that they really are
charming phasmids, and I thoroughly encourage the majority of you to consider
adding some of the Pseudophasmatinae to your collection.
Shortly
after I wrote this article, my whole culture of Alloeophasma cyllarus
died within a few hours of one another. They
became listless, then fell to the ground twitching and jerking.
These symptoms are indicative of pesticide poisoning, and indeed, I had
just that day replaced their food. However
I am a little confused, since I used the same source of (untreated) privet as
always, and washed the leaves as usual before feeding them to my collection. Moreover, I had that same day placed privet from the exact
same source into several other of my tanks, some of which contained young
nymphs. Yet none of these other
phasmids appeared to suffer. If
anybody has any suggestions as to what went wrong, I would be grateful to hear
from you. E-mail: sally.ewen@talk21.com
Regarding
Anisomorpha ferruginea, I expect to be able to bring some along to the next PSG
meeting, should anybody be interested.
1
Brock,
Paul D.,
The Amazing World of Stick and Leaf insects
Thank
you very much to Timm Reinhardt who was kind enough to proof read my article and share
with me his knowledge of many aspects of Pseudophasmatinae-keeping.
Timm also suggested that my A. cyllarus culture may have been
poisoned by new growth on the tips of the privet shoots; I shall thus aim to
feed only mature privet leaves to phasmids.