Phormictopus Species Husbandry

Awesome intermediate species tarantulas with plenty of character.

Anyone that follows me on Tom’s Big Spiders, Tumblr, or YouTube has probably picked up on my Phormictopus obsession. I currently keep seven different Phormictopus species, and I am attempting to acquire all the species and color variations available. These spiders have quickly risen to the top of my list of favorite terrestrials. and I’m looking very forward to some future breeding projects with them.

But why the fascination?

I first encountered this genus while perusing the Jamie’s Tarantulas website for something new and interesting. She had just listed some Phormictopus cancerides or “Hatian Brown” slings for sale, and something about them caught my eye. At this point, I had a much smaller collection, and the majority of the specimens I was keeping were the more docile beginner terrestrials. I decided to do some research, and I discoved that most described the P. cancerides as a large brown, ornery tarantula with a bad attitude.

Phormictopus sp. purple

Phormictopus sp. purple

Large and brown? Having just acquired an A. versicolor and two C. cyaneopubescens, I was on the market for more colorful tarantulas. The idea of a “blah” brown spider didn’t quite appeal to me. Of course, after some investigating, I learned that males from this species were a gorgeous purple, and females were more a metallic bronze. This was far from just a big “brown” spider.

P. cancerides female

P. cancerides female

Ornery with a bad attitude? THAT, on the other hand, caught my attention. Most of the Ts I kept were quite calm and well-behaved, and I felt that it was time for me to graduate to something a bit more spirited and “advanced”. The idea of a larger, more feisty spider appealed to me.  It wasn’t that I necessarily wanted to add a giant eight-legged terror to the collection, but I felt I was ready for the challenge if this species turned out to be less than friendly.

In my research, I also learned that this species apparently “required” moist substrate, which was a husbandry requirement that I hadn’t yet contended with. As I had my eye on some Asian terrestrials down the road, this would be a good stepping stone to keeping spiders with more complicated husbandry.

Beautiful blue slings with vicious appetites

After a week or so of research, I decided to pull the trigger and order two P. cancerides slings. When I unpacked them, I was immediately amazed by the color. These two little 1.25″ slings sported a gorgeous a metallic blue sheen that looked nothing like the supposed “brown” tones sported by their adult counterparts. I rehoused each and, as is usually my habit, I offered each its first meal.

And I instantly fell in love.

I watched in awe as one of these gorgeous blue slings bolted across the enclosure and LEAPED on a cricket with so much force that it actually rolled over onto its back for a few seconds while it wrestled with the bug on top of it. I had never seen anything like it. I quickly fed the other and was delighted to discover a similar response.

P. atrichomatus sling

P. atrichomatus sling

Since then, I’ve discovered that all of my Phormictopus species attack their prey with the same fervor, and it honestly never gets old to see one of these guys launch itself at a roach or cricket.

As slings, Phormictopus species do appreciate deep, moist substrate, and the majority will burrow if given the opportunity. For substrate, I use a mix of topsoil, peat, and some vermiculite, and I keep it moist enough that it will hold its shape when squeezed but no water will drip out. As the spiders become established I let the top layers of the sub dry out a bit. This allows the T to burrow to the more moist depths to find the correct humidity level. If I need to add water, I’ll use the end of a paintbrush to carefully put some holes down the side of the enclosure and allow the water to filter down to the lower levels.

Phormictopus sp. purple sling

Phormictopus sp. purple sling

As slings, these guys are voracious eaters. During this period I will feed them 2-3 times a week, depending on the size of the prey. Unlike other species, I’ve found that Phormictopus have no trouble taking down larger prey, so I will often give my little ones crickets that aren’t much smaller than they are. They have only ever refused a meal when in heavy premolt, and even then I had one eat just a couple days before molting.

Get ready for an amazing growth rate

As I’ve stated in my other husbandry articles, my spiders are kept between 70-76° in the winter and about 75-80° in the summer. Although higher temps would obviously lead to faster metabolisms and growth, my Phormictopus species do very well in these ranges. Not only is this a species that will molt very regularly (at one point, mine were molting about every 5-6 weeks as slings), but the amount of size they gain between molts is amazing. After keeping slow-growing Brachypelmas and Grammostolas for a while, I was floored when my P. cancerides slings first molted, putting on about .5″ of size as well as impressive girth.


Although I started off with small slings, it didn’t take too many months or molts before I had large, hairy bronze spiders. In their first year, my 1.25″ P. cancerides slings reached about 3.5″ in size. Imagine the growth rate if they were kept at higher temps. On the other hand, my 1″ Phormictopus sp. purple slings grew from about 1″ to a leggy 3.75″ (I’m sure the fact that I bought them closer to the summer had something to do with the slightly faster growth rate). So far, my atrichomatus specimens, which I purchased in April as 1.25″ slings, are about 2.75″ or so.

Once mine hit about 2.5″ or so, I slow down the feeding schedule. I currently feed my juveniles a large cricket every five days. For my sub-adult specimens, they get a couple large (1-1.5″) dubia roaches once a week or so. If I have extra large crickets, I’ll sometimes toss a couple in as well for variety.

Housing for Phormictopus species

Due to the fast growth rate, I tend to house my Phormictopus species in larger enclosures than I would for other species. As slings, I usually use 2-quart clear plastic jars or the small Sterilite stackables containers (I believe it’s about 1.75 quarts or so). After filling them up with moist substrate, I supply them with a bottle cap water dish, a cork bark hide with a plant, and a starter burrow.


2-quart plastic canister (purchased at WalMart for about $2)

Although enclosures this size might seem a little large at first for a 1″ sling, they grow fast and need a bit of extra space to eliminate the need for frequent rehousings. Trust me, they will quickly grow into their new homes.

Small Sterilite stackable container.

Small Sterilite stackable container.

Once my guys reach about 2.5-3″ or so, I will move them to their juvenile enclosures. For these, I use Sterilite clear plastic shoeboxes and set them up more like a terrestrial. They’ll get about 3″ of moist substrate, a cork bark hide, and a water dish. I find that at this size, my Phormictopus have become more bold and will mostly hang out in the open. They no longer burrow, but will retreat to a hide if disturbed.

My Phormictopus sp. blue female's enclosure (a clear Sterilite shoe box)

My Phormictopus sp. blue female’s enclosure (a clear Sterilite shoe box)

My largest specimens (5″ or over) are currently housed in Sterilite 15-quart “ClearView” containers (purchased at the local Target). Once again, they are set up terrestrially with cork bark hide, water dish, and 3-4″ of damp substrate.

Although a lot of the early care information I read about Phormictopus indicated that they needed to be kept moist, I’ve discovered that they do fine if the sub dries out a bit in between as long as they are provided water dishes. Although I start all of mine on moist sub, I let it dry out a bit and periodically moisten down part of the dirt when they are near a molt. I’ve noticed that they don’t seem to gravitate to this moist area, and are quite content to sit on the dry end.

I will note that other keepers still make sure to keep their Phormictopus species moist at all times, and those interested in breeding are often much more careful in keeping the moisture levels up.  However, unlike my Pamphobeteus and Theraphosa, I don’t obsess about it with these guys. If you buy one of these species and the enclosure dries up a bit, they will be fine as long as they have water.

A note about temperament

Phormictopus species have developed a bit of a reputation for being a bit ornery and defensive. I’ve found slings of this genus to be quite fast and skittish, often bolting around their enclosures or to their burrows if disturbed. As they gain some size, they become a bit more bold, often sitting out in the open when their enclosures are opened. Still, they can move quite quickly when motivated, and I’ve heard of instances where they are not reluctant to use their fangs.

Phormictopus sp. Purple

Phormictopus sp. Purple

Out of the seven species I currently keep, I’ve only ever received a threat posture from my sp. purples; they seem to be a bit more high strung than my other species. Personally, I’ve found that if I’m careful not to disturb them when I perform maintenance or feed them, they are relatively calm when they get older. They also seem quite reluctant to kick hairs, which is a huge plus in my book. To date, only one has ever kicked hairs that I’ve witnessed.

Still, these guys get pretty large, with some reaching 8″, and their amazing feeding responses often have them charging anything that enters their enclosure (including a keeper’s tongs or paint brush). Caution should be exercised whenever feeding or performing routine maintenance.

A wonderful stepping stone to faster and feistier species.

For those who have successfully kept some of the beginner species and are looking to graduate to faster, more defensive intermediate species would do well to check out some of the  spiders the Phormictopus genus has to offer.  These are large, hardy,  fast-growing tarantulas with relatively simple husbandry that are very similar to the super-popular Pamphobeteus species in terms of build and temperament.

It’s also worth mentioning that males of these species are often quite colorful, with some sporting beautiful purples and blues after their ultimate molts. This makes discovering that your spider is a male quite a rewarding experience…after all, who doesn’t like purple spiders?

Phormictopus species I currently keep:
  • Phormictopus cancerides
  • Phormictopus sp. purple
  • Phormictopus sp. green
  • Phormictopus sp. blue
  • Phormictopus atrichomatus
  • Phormictopus cautus violet
  • Phormictopus sp. south hispaniola

Sexing Tarantulas Using Molts

For most tarantula keepers, females are where it’s at.

It’s not that we don’t have love for their male counterparts. In fact, some male species like Phormictopus and Pamphobeteus are more colorful and stunning than the females. No, in most instances, the reason comes down to longevity and their ability to produce young. Female tarantulas are much more long-lived than their male counterparts, often thriving decades after the males have matured and expired. Females can also be bred to produce slings, an integral and fascinating part of the hobby for many.

The story is a bit different for male tarantulas. Some species of male tarantulas can mature in just over a year, leaving you with a leggy, antsy boy who wanders around his enclosure in a desperate attempt to fulfill his life’s goal to mate with a willing female. At this point, the best thing you can do for this tarantula that you have lovingly raised and cared for is to ship him off to someone with a female for breeding, leaving you with an empty cage. Sure, you can do do a breeding trade for half of the slings a successful pairing produces, but not all attempts end in viable sacks, and some end with the male being unceremoniously munched.

Those who enjoy raising tarantulas (and who don’t feel like paying the higher prices for sexed females) will often pick up spiderlings. As small slings are often difficult, if not impossible, to sex accurately, you never know exactly what you’re getting when you pick up a tiny spiderling. Many keepers (myself included) will pick up three or more slings of the same species at a time to increase their chances of getting a female. You then feed them, love them, and watch for signs that you might have hit the spider jackpot with a female.

Female C. cyaneopubescens molt (GBB)

Female C. cyaneopubescens molt (GBB)

Sometimes you notice one growing faster than the others, and immediately suspect a male. After all, males in many species will grow and mature faster. Other times, you see the spider’s underside pressed up against the side of its enclosure and you swear you see female parts. And still others, you’ll latch on to some physically dimorphic feature, like color or patterning, in hopes that it indicates a female.

Any keeper who has patiently waited to sex a spider they have raised from the sling stage has undoubtedly experienced the thrill of discovering they have raised a young lady … or the letdown that their beloved pet is a more short-lived male.

How do you sex a tarantula?

There are several methods keepers to use to determine the sex of their tarantulas, but many are not very accurate or require the keeper to have plenty of experience as well as a keen understanding of the anatomy of many species.

One method used to sex tarantulas is ventral sexing, which entails examining the tarantula’s ventral area (the bottom of the tarantula) around the epigastric furrow to try to determine its gender. The epigastric furrow is an opening between the set of book lungs closest to the cephalothorax (body) of the spider. Folks using this method will compare the curve of the furrow, the distance between the anterior book lungs, and the angle of the lungs to determine gender.

In females of some species, the epigastric furrow is more pronounced with what can be described as “lips”. In others, it is not nearly as pronounced. This method takes plenty of practice and knowledge of what both the female and male characteristics of each species are. Keepers attempting this technique will want to do some research and get some photos of both males and females for comparison.

A ventral shot of an A. insubtilis. This specimen was likely male.

A ventral shot of an A. insubtilis. This specimen was likely male.

Personally, I don’t even try to sex via ventral shots anymore, as I don’t feel that I’m particularly good at it, and it’s often not very accurate. Sure, some species like some of the Poecilotheria sport some fairly obvious lady parts early on, but others can be quite misleading and difficult to determine. Arachnoboards has a wonderful area where keepers can post ventral shots of their Ts so that others can determine the sex, but due to the trickiness of using this technique, many of the responses are just guesses (as evidenced by the same spiders being proven to be a different sex later on). Still, if you attempt this method, try posting a good ventral photo up on this board to get some other opinions.

There is also the epiandrous fusillae method.  With this technique, the keeper looks for epiandrous fusillae, or a second set of micro spinnerets used by mature male tarantulas to create sperm webs.  This is a technique that requires a keen eye and a lot of practice, so it might not be the most appropriate for some keepers, especially those new to the hobby.

Sexing your spider using the molt

The best way to your tarantula is to examine its exuvia or molted exoskeleton. An intact molt from a larger specimen (smaller specimens may require use of a microscope) can be examined for evidence of the female’s spermathecae, or the receptacle the female that stores the male’s sperm in. This organ is often described as a little “flap” or “pouch” above the epigastic furrow.

Although this method can be tricky at first, especially with smaller specimens, it’s the most accurate and easy to practice. All you need is an intact molt, some good lighting, and you can give it a shot. Here’s how to go about it:

A comparison of molts from a 3.5" male and a 3.5" female T. stirmi. The piece of paper on the female molt is showing the "flap".

A comparison of molts from a 3.5″ male and a 3.5″ female T. stirmi. The piece of paper on the female molt is showing the “flap”.

1. First off, you’ll want to do some research and find reference photos for both a male and female of the species you want to sex. I would encourage folks to hop on Arachnoboards’ Tarantula Sexing board and check out some of the shots there, or do a Google or Bing image search and study some of those. Every species is different, so looking at a molt from a L. parahybana might not be useful for determining the sex of a GBB. 

2. Next, you need a molt that has the abdomen flesh containing the book lungs intact. If the abdomen has been completely shredded in this area, you will find it difficult or impossible to sex the molt. I try to grab the molts from spiders I want to sex right after they molt (as long as I can do it without disturbing the tarantula). 

3. You need to soften up the exuvia, or molt, to make it less fragile and more pliable. I use a very small spray bottle and give it a few squirts. I then wait a few minutes for the molt to soften up. Other folks will drop the molt into a dish of warm water for a minute or so. Either of these methods work, just use care when handling the molt not to tear it or get urticating hairs on you. You may also want to put it on a piece of paper towel to wick up some of the excess water.

4. Position the molt so that the fangs are facing up and the molt is on its “back” on your well-lit working area. I like to use white plates myself, but a piece of foam board would be great if you want to pin the molt down. Now, carefully spread out the legs and unfurl the abdominal skin if it has become twisted. Work slowly and carefully, as the area that you need to sex the molt is VERY fragile and will tear. I will usually use toothpicks and cotton swaps to unfurl mine. You want to open up this abdominal skin so that you can see the underside of the area where the two sets of book lungs are.


5. Now, some folks will immediately spot a slit between the set of book lungs closest to the body and think that they have a girl. Not so. This slit is found on both males and females. What you are looking for is a pronounced “flap” or the spermathecae, which will be above the epigastic furrow if present. The smaller the specimen, the more difficult this area can be to see. I often use a magnifying glass or take a close-up photo with my phone to get a better look. On well-developed females, you can even take a small piece of paper and slide it behind the flap to be sure.


If you find the spermathecae, congratulations … it’s a girl! If not, and you are sexing a largerer specimen, you are likely looking at a male. You can always try again on a future molt to double-check.

Now this all sounds quite simple, but it’s not always that cut and dry. Some species don’t develop enough for the casual keeper to sex until later in their life cycles. Also, males from some species will have organs that can be mistaken for spermathecae, meaning that sexing those species can be a bit more challenging. If you are trying to sex your pet, you should spend some time researching and examining molt photos from both the males and females of the species. For some wonderful reference diagrams of the spermathecae of females from different species, check out this site. A Google search will also bring up several useful photos, and you can also check the sexing topic on Arachnoboards and compare the photos.

L. itabunae female molt with the spermathecae highlighted.

L. itabunae female molt with the spermathecae highlighted.

Recognizing mature males

It should be mentioned that mature males can be quite easy to sex, and you will often hear keepers refer to their males as “hooking out.” This expression comes from the fact that males from some species develop tibial “hooks” behind the knees of their first set of walking legs upon maturing. The key word here is “some”, as many species will not present this feature while others, like some in the Avicularia genus, will have hooks too small to see.

An illustration of a male tarantula. Some species don't have tibial hooks, so it is better and more accurate to look for the emboli.

An illustration of a male tarantula. Some species don’t have tibial hooks, so it is better and more accurate to look for the emboli.

Honestly, the phrase should be changed to “bulbing out” or something similar, as keepers should be keeping an eye out for another telltale feature; namely the bulb-like emboli at the end of the male pedipalps. The pedipalps are the shorter set of appendages inside the first set of walking legs that look like shorter legs. When a male spider has his ultimate molt, he develops emboli, or essentially the male’s sexual organ used to deliver the sperm to the female, on the end of his pedipalps. Instead of the ends of these appendages looking like the rest of the tarantula’s “feet”, they will instead be round and bulbous (some keepers refer to them as “boxing” gloves).

A comparison of a mature male's pedipalps (with emboli) and a mature female's.

A comparison of a mature male’s pedipalps (with emboli) and a mature female’s.

Because all male tarantulas will develop this feature, it makes more sense to look for emboli when trying to determine if your spider is a mature male or not.

Not only do males mature much faster than their female counterparts, but there are often many physical differences between a male and female of the same species. First off, males tend to be thinner and “leggier” than the girls, who are much more heavy-bodies. Many male tarantulas have different colorations than females, with some being very pronounced. Female L. violceopes, for example, sport gorgeous iridescent blues and purples upon reaching maturity. Males, on the other hand, are brownish to olive in color. Some males also mature at a much smaller size than the females of the same species; this can lead to some confusion for keepers who discover that their gangly male is done growing at 5″ and will never reach the 7″ max size of the females they’ve read about.

Unfortunately, many of these features won’t appear until the specimen’s ultimate molt, so those using this “method” would literally be discovering their pet’s sex at the latest possible opportunity.

Lots of practice is required!

No matter what method you choose to try to sex your specimen, research and practice are key. I have literally examined over a hundred molts now and spent countless hours staring at sexed molts on my computer screen. And although I feel like I’ve definitely got the hang of it, I still have difficulties at times. I’m certainly not yet an expert yet. When you’re first starting out, be sure to try and sex every molt you can. Do you have specimens that are already sexed male or female? If so, examine and photograph their molts as practice and to use as references.

With all of the variations between species, it can be very difficult to know what to look for. I would encourage anyone attempting to sex their T to look up the species first and find out all you can about it’s anatomy or any sexual dimorphism. Some questions you should be researching are:

Are their differences in colorations, marking, or bandings between the sexes?

Is this a species that can be sexed ventrally with accuracy?

What is the shape of the female’s spermathecae?

At what size to the genders become apparent enough to accurately sex by molt?

Does the male of this species have an organ that could be mistaken for a spermathecae?

Does the male of this species have tibal hooks?

Sexing may seem daunting and confusing at first, but with enough practice, most keepers will be successfully identifying the genders of larger specimens in no time. And honestly, the first time you examine a molt and discovering that the sling you have raised for a year is a little lady makes all of the effort and frustration worth it.

* Note: I will continue to update this blog with photos of sexed molts. It’s my hope that this can be a resource for some looking for reference photos.