FROGS
Frogs of the family Dendrobatidae are commonly known as Poison Frogs
or Dart-Poison Frogs, since are used by natives of the Choco region of Columbia
to poison blowgun darts used for hunting birds and mammals.
Seven genera of Anurans have been discovered to contain potent alkaloid toxins on the skin :
4 genera are in the family Dendrobatidae:
genus Dendrobates, Epipedobates, Minyobates and Phyllobates;
the other 3 genera being:
Mantella [Madagascar], Melanophryniscus [South America] and Pseudophryne [Australia].
The skin of such Amphibian has provided over 400 alkaloids of over 20 structural classes;
these include the batrachotoxins, histrionicotoxins, pumiliotoxins and epibatidine .
Batrachotoxin, the most powerful animal venom known
 [250 times more powerful than strychnine],
is produced by the dart-frog Phyllobates terriblis.
[Daly, J.W., 'Thirty years of discovering arthropod alkaloids in amphibian skin', 1998, J. Nat. Prod., 61(1), 162-172;
Daly, J.W., Myers, C.W. & Whittaker, N., 1987, Toxicon 25(10), 1023-1095;
Daly, J.W., 1995, 'The chemistry of poison in amphibian skin', Proc. Natl. Acad. Sci. USA  92, 9-13; ]
The minimum lethal dose of the batrachotoxin in a 20-gram mouse is 0.05 mg;
the amount of toxin/frog-skin averages 1,100 mg;
a single P. terriblis has enough poison to kill upwards of 20,000 mice, or 10 to 100 humans
 http://www.bio.davidson.edu/Courses/anphys/2000/Todd/ecology.htm ;  http://pilot.msu.edu/user/costabil/academic/portfolio/herp-lab/ Anura.htm ]
 http://www.luminet.net/~chdavis/frogs/poison.htm
 http://www.sandiegozoo.org/wildideas/animal/amphibian.html
There exists over 165 different types of arrow-poison frogs
[http://www.discovery.com/cams/frog/learn.html].
Epipedobates tricolor is one of  the most poisonous frogs known,
being capable of knocking out a huge water  buffalo.
[http://www.abdn.ac.uk/chemistry/abt].
The highly toxic alkaloid called epibatidine, isolated from the skin of this Ecuadorian tree frog,
produces muscle paralysis and cardiorespiratory depression, eventually leading to death
[Marwick C, 1998, J. of Am. Med. Ass., 279(21): 1679-81]

SNAKES

Of 100,000 snake bites in the United States over the past years, only 12 resulted in fatalities
[mostly in children, the elderly, members of religious sects] http://www.merck.com/pubs/mmanual/section23/chapter308/308a.htm] ,
while more fatalities result in Africa: 1,000 deaths; in Brazil, Ecuador and Venezuela: 3,000 deaths;
in India and Pakistan: 8,000 deaths; and in the Middle East: 20,000 deaths.
About 450 of the 3000 species of  venomous snakes
are considered poisonous to humans.
The most important are listed below, by common names:

Statistics also reveal that of snakebite victim deaths,
17% died 1 to 12 hours after being bitten
and 64% between 12 hours and 2 days.
[ University of Florida, Institute of Food and Agricultural Sciences (UF/IFAS)]

Sub-cutaneous LD50 of 20 most poisonous snake venoms,
according to B. G. Fry
[ http://www.kingsnake.com/toxinology/BGF/BGF.html ]

ARTHROPODS
Apids [honeybees, bumblebees],
vespids [wasps, yellow jackets, hornets],
and Ants

In the USA, stings cause 3 to 4 times more deaths than do venomous snakebites.
Millions of people in the United States are injured from venoms produced by insects
and other arthropods each year. Of these injuries about 25,000 result in severe injuries
and about 32 result in deaths.
The average person can safely tolerate 10 stings/lb body weight;
the average adult can withstand >1000 stings,
whereas 500 stings can kill a child.
However, one sting can cause a fatal anaphylactic reaction in a hypersensitive person;
more often, toxic reactions to Arthropods venom components,
may manifest clinically as anaphylaxis,
after 50 to 100 stings.
Insect stings result in rapid progression of toxic effects.
Of 208 deaths, 80% occurred
less than one hour after being stung by Hymenoptera
(bees, wasps, yellow jackets, or hornets).

Imported fire ants account for two thousands of stings each year .
There are several fire ants species, but Solenopsis invicta predominates
            and is responsible for an increasing number of allergic reactions.
In infested urban areas,
as much as 40% of the population may be stung each year.
Fire ant venom has hemolytic and cytolytic properties.
Anaphylaxis due to fire ant stings probably occurs in < 1% of patients.

Average Deaths from Venomous Pests

The best known neurotoxins produced by spiders

SCORPIONS
Although there are over 1050  different species of scorpions world-wide,
relatively few of them are poisonous to man.
One such highly poisonous scorpion is the Leiurus quinquestriatus
found predominantly on the Israeli deserts.
Also called the 'Death Stalker' or  'Yellow Scorpion',
Leiurus quinquestraitus produces one of the most potent venoms of all scorpions.
It has an LD50  of about 0.3 mg venom/kg mouse
compared to an LD50 of 1.45 mg venom/kg mouse
in the Mesobuthus eupeus scorpion of Iran.
The main neurotoxins of the Leiurus quinquestriatus venom are chlorotoxin and charbydotoxin
[http://www.portfolio.mvm.ed.ac.uk/studentwebs/session2/group13/scorpions.html]
The scorpion Tityus serrulatus produces the neurotoxin tityustoxin
[Romano-Silva et al., 1994, Biochem. J., 304, 353-357].
The venom of  Centruroides exilicauda (sculpturatus),
causes immediate pain and some numbness or tingling over the involved part.
Children become tense and restless, display abnormal and random head, neck, and eye movements.
In adults, tachycardia, hypertension, increased respirations, weakness,
and motor disturbances may   predominate.
Respiratory difficulties may occur in children and adults, often complicated by excessive salivation.
C. exilicauda stings have resulted in death in children < 6 yr and in hypersensitive persons.

The most studied toxins of Scorpions

MARINE ANIMALS

There are over 500 species of cone snails, marine animals found in  coastal areas.
Each species produces many different venoms .
The venoms of Conus geographus are fatal to humans 70% of untreated cases.
Conotoxins, the most potent neurotoxins produced by C. geographus,
are small peptides, normally only 20-30 aminoacids in length.
[http://www.biology.utah.edu/people/regfaculty/~goldenberg/GoldenbergLab/research/co]
Coelenterates are responsible for more envenomations than any other marine animal.
Of the 9000 species, about 100 are toxic to humans.
Coelenterates, including the corals, sea anemones, jellyfishes, and hydroids (as Portuguese man-of-war),
have a highly developed stinging unit (the nematocyst) that  can penetrate human skin.
Systemic  manifestations include weakness, nausea, headache, muscle pain and spasms,
lacrimation and  nasal discharge, increased perspiration, changes in pulse rate, and pleuritic chest pain.
In North  American waters, the Portuguese man-of-war has caused several known deaths.
Members of the Cubomedusae order are the most dangerous of coelenterates,
particularly the sea wasp Chiropsalmus quadrigatus
and the box jellyfish Chironex fleckeri
have been responsible for several deaths in Indo-Pacific waters.
The Box JellyfishChironex fleckeri, also known as sea wasp, sea stinger
is higly lethal to humans: death within 5 minutes is possible.
 http://www.usyd.edu.au/anaes/marine_enven.html

Birds
"Three passerine species in the genus Pitohui,
endemic to the New Guinea subregion,
contain the steroidal alkaloid homobatrachotoxin...
Toxin concentrations .. are highest in the skin and feathers."
Some homobatrachotoxin is also present in muscle tissue.
[Dumbacher et al., 1992, Science 258, 799-801]
Homobatrachotoxin is one of the most toxic neurotoxins, collectively called batrachotoxins,
produced by the most poisonous dart-poison Frogs of the genus Phyllobates .
The most toxic species is Pitohui dichrous;
less toxic are P. kirhocephalus and P. ferrugineus.
The death of laboratory mice injected with skin extracts of Pitohui
does occur within 18-19 minutes,
as if injected with 0.05 µg of homobatrachotoxin.
[Dumbacher et al., 1992, Science 258, 799-801]