Over my 30 years of keeping tarantulas alive in vivaria, I must admit to having been fooled many times both by the spiders themselves and by my well-meaning colleagues or so called "experts", who claimed to have discovered some foolproof method of accurately determining the gender of individual tarantulas.
Well, if those techniques were indeed "foolproof", then I must be nobody's fool, since they have proven to be about as but no more accurate as flipping a coin. Heads is female, tails is male. The author has heard everything including a few you may have missed!
This includes being told, "the bigger one is the female" or male, as the case may be, until my face is bluer than a Haplopelma lividum' s legs! Invariably, the "female" will molt out with tibial hooks and palpal emboli and the much needed "male" that you raised from a spiderling will continue to molt out every year with nary a sign of maleness. All this from the prophets of theraphosid prognostication, who SWORE that the spider must be a male because its "such and such was so and so".
Alas, was there no True Science in the muddled forest of Pseudoscientific methods and outright chicanery?? Fortunately, for those of us who breed tarantulas regularly, the technique of sexing theraphosid spiders from the microscopic examination of the exuviae shed skins , is a True science. Our colleagues in the British Tarantula Society, especially John and Kathleen Hancock, brought this valuable technique for accurately sexing tarantulas to light in their book entitled, "Tarantulas: Anyone with access to a light microscope could be fairly certain of the sex of their tarantulas when an exuvium became available.
This technique is very important, and one which every serious tarantula breeding MUST learn, to ensure the long term planning and availability of males for future breeding projects. Unfortunately, this technique has its limitations. I mean, what does one do when standing in a pet store or at a breeder's table at a show, with onlookers pressing up against you? Try saying "Excuse me, Mr. Pet Store Owner, did you happen to save the last shed skin from this particular Brachypelma smithi?
Oh, and do you happen to have a stereoscopic microscope that I might borrow for a moment? Also, in home collections, even for those who keep meticulous records, it is possible to get skins confused when taking dozens of molts from dozens of cages over dozens of days. Thus the quest remained for a reliable method based on scientific evidence that allows one sending out DNA samples was not reasonable to immediately determine the gender of a live tarantula.
Pouring over endless volumes of foreign texts, in Germany, French and Portuguese, had led me to the conclusion that they might have stumbled onto some technique. Further investigation and expensive translation software! All were merely educated guesses, based on many, many years of experience and looking at many thousands of spiders, most of the same species or two. But what about the lone tarantula in a "Critter Cottage" in the corner of a pet shop on Main Street?
Or the lone specimen of a rare species that you need to pair up and there is only one large juvenile in the dealer's display case and he swears that it is the exact sex you need? Where was Science then, to help prove the dealer to be honest or expose the truth? But this endeavor was not to go unrequited forever. During the long, hot summer of , I was fortunate enough to attend the "Invertebrates in Captivity" Conference of the Sonoran Arthropod Studies Institute, held annually in Tucson, Arizona.
Edwards of the Florida Department of Agriculture, Dr. Robert Wolff of Trinity College and a list of others too numerous to mention. Surely the answer to the timeless question of theraphosid gender determination would be answered definitively here, and we were NOT to be disappointed.
Rick had been coaxed from his home in the idyllic Canadian Northwest to come and give a two day "mini Seminar" on theraphosid spiders. While the SASI conference covers ALL Arthropods, most of the over attendees were, at the very least, passingly interested enough in tarantulas to make the seminar a worthwhile event on its own.
Rick's seminar was to cover two main areas. The first was the presentation of his illustrated Keys to help hobbyists and invertebrate specialists identify theraphosid subfamilies and some genera and the second part was to demonstrate the easy method of sexing living tarantulas. For those not familiar with Rick West or his work, Rick is one of those rare individuals whose thirst for personal knowledge has caused him to acquire vast numbers of sometimes obscure papers on various things arachnological.
This, coupled with Rick's own encyclopedic knowledge of the subject of tarantulas was to lead to this breakthrough in the community of tarantula enthusiasts. This paper is about spider spinnerets, of all things, and made references to certain fusilla or spinnerets that are found only on male spiders, called epiandrous fusillae. According to the paper, nearly all male spiders, including all tarantulas, have this extra set of silk spinning glands and fusillae or spinnerets.
If only we could find them on a spider, we could at last determine, conclusively and through Science, whether the spider was male or not male i.
Apparently, almost all male spiders, including all theraphosids, have this extra set of silk spinning fusules or tubes that are connected to epiandrous glands. It is believed the epiandrous glands produce a special silk used in the construction of the sperm web, a structure only built by male spiders in aid of transferring seminal fluid from the genitalia to the palpal bulbs.
In addition to this paper was a page of illustrations presented and reproduced, in part, by Mr. These illustrations more clearly showed the location and appearance of the structures in question on a tarantula. As can be seen by the drawings, and in conjunction with the text by Mr. Marples, the epiandrous fusillae are positioned on the central anterior edge of the males epigastric furrow. A detailed chart on sexing tarantulas may be downloaded here.
You may download it for free from here. They occur in between 2 and 4 rows and form a semi-circular or sometimes triangular shape that suggests an "arch" of more dense, shorter, darkened hairs or setae. The Aphonopelma chalcodes Chamberlin, pair pictured above are about the same size and shape, however one of them is an about-to-mature penultimate MALE.
Care to take a guess? Let's turn them over and take a look. On larger spiders, the presence or absence of the epiandrous fusillae is generally visible to the naked eye, although a good light source is recommended.
With smaller tarantulas, down to a size that can be safely picked up and turned over i. Further examination of molted skins reveal that the epiandrous fusillae are visible on even very small spiderlings. One is male and the other female.
Shall we look and see? These spiders also have light colored undersides. One has to ask, then, how did the tarantula-keeping community overlook such an obvious characteristic for so long?
Though it is impossible to know with certainty, one might hazard a guess. It is undoubtedly true that the average tarantula keeper not breeder is almost always on the lookout for a FEMALE tarantula.
The fact that they are larger, more massive and live far longer in captivity all add up to the choice of a female being the wiser decision and choice over a male. Except for breeding, the male is a poor financial investment for the average tarantula keeper. This Mexican Fireleg appears to be a female; no hooks or palpal emboli. But let's take a look underneath This is the view from underneath.
What do you think now? The magnified photos figured in this article should help illustrate the appearance and location of these silk-producing hairs that appear like short, stiff and slightly bent hairs. Under high magnification, these hairs take on the shape of an arch or inverted triangle in some species such as Pamphobeteus and Megaphobema.
On the underside of some tarantula species, such as Aphonopelma seemanni F. Click the images to enlarge. With some practice and a pocket microscope for the smaller spiders, sexing tarantulas can be simple. Use care when handling your spiders! The gender of your spider is moot if you kill it in the process. On these aforementioned tarantula species, they have light orange to peach colored epiandrous fusillae, which blend with the same surrounding colored hairs.
This error could easily cause one to look upon all hairs on the anterior epigastric region as epiandrous fusillae, erroneously leading one to believe all tarantulas are males. Naturally, time and practice are required. If done on a live tarantula, such as a Haplopelma or Pterinochilus or any of a number of fast and aggressive tarantulas, there are inherent risks of an entirely different nature, which require a modicum of skill and a pair of forceps.
The author uses forceps clamped ventrally along the carapace between the 2 and 3 legs. We recommend a firm grip and a prayer! Many of the larger arboreal species can be positively sexed while they are posed against a glass or plastic wall, given sufficient light, a keen eye and a magnifier.
In the beginning, you are apt to make a mistake or two and the level of ones eyesight mine is rather poor can also add to or detract from the success you will have with this method. Take the time and work on it, if you care.
Learn to do it yourself! Of the several hundreds perhaps thousands of live tarantulas the author has sexed since the demonstration by Rick West, there've been very few challenges as to the accuracy of this tarantula sexing method. So get to work! The contents of this page, all subsidiary pages, and all associated graphics elements are covered by international copyright and may not be reproduced in any form without the express written consent of the authors.
Additionally, although Rick West keeps up with taxonomic changes scientific names change constantly and may not always be immediately reflected on this website. All materials contained herein are the property of Rick C. Unauthorized duplication, be it electronic, mechanical, photocopying, recording or otherwise will be prosecuted to the fullest extent of the law.