On Insect cocks

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Cock. Penis. Dick. Wang. Whatever you call the male appendage, this is an area of insect physiology where things get pretty wild. Or perhaps more accurately, wilder than the usual.

But let’s start scientifically-correct: in the insect world the closest thing to the human penis is more properly known as the aedeagus. But ‘closest thing’ does not in any way imply great similarity. It’s actually part of the insect abdomen, and the external part of the male’s sexual weaponry is a phallus of extremely various flaps, hairs and hooks. Still with this? Good.

When it comes to shape, describing the situation as complex doesn’t get anywhere near to doing it justice. Menno Schilthuizen’s account of genital evolution is a comprehensive overview (far more so than can be included here), highlighting a wonderfully alien world of ‘prongs’, ‘pegs’, ‘springs’ and ‘titillators’. If insects are purely in it for the passing of genes, they could’ve fooled us.

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Amazing aphid dicks: from Wieczorek et al, 2011 

There’s so much to say about the morphology of aphid appendages alone that the main journal paper on the matter comes in two parts. For relatively small insects, aphids come with a significant package – “relatively large and discernible under a hand lens or even with the naked eye”. The paper includes such descriptive gems as “a few circular pits distributed mostly in its medial part. Sclerotized arms with distal part rather long and thin, and proximal part shorter and wider. Aedeagus long, inverted question mark-shaped.” And that’s just the aphid Drepanosiphumplatanoidis. Big name, big aedeagus.

Smutty jokes aside (but not for long), in insect taxonomy, male sexual organs can be extremely helpful in establishing exactly what species you’re dealing with. In fact, it can often be the only way of making a certain identification. So far, so useful, to us as well as them. But how do insects actually, you know, do it? Again, this is no simple matter.

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Normal for dragonflies: from Miller, 1991

The ‘lock and key hypothesis’ is an idea that has persisted in entomology – and, naturally,
argued over. It asserts that male and female sexual organs of an insect species, whatever wacky shape and size they are, have evolved to only be the exact ‘fit’ for each other. The theory, however, has been largely discredited over the years.

What’s abundantly clear is that sex is rarely anything straightforward in the insect world – there’s little by way of proxy for missionary. Dragonflies are a good go-to example for the messiness of it all – so much so that their sexual antics inspired a New York Times article, in which the slaty skimmer (Libellula incesta) is described as having a “fairly rococo penis”. Sex begins with what constitutes foreplay – the male grabbing the female at the back of the head – while dragonfly dongs are not just about depositing sperm, they’re also about removing that of rivals. Naturally, females are tooled up to stop that happening, if at all possible.

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Brutal bruchid beetle bell-end: Wikimedia Commons

The mealworm beetle (Tenebrio molitor) also has a dick geared up to dispatch the genes of its rivals. In the words of this paper on the matter, it “comprises a central shaft enclosed within a flexible sheath covered with chitinous spines. As the shaft extends within the female’s copulatory bursa the sheath and its covering of spines rolls back producing a `scouring’ effect.” Lovely.

With schlongs often more resembling torture implements, things can get even more brutal. Males of the bruchid beetle (Callosobruchus maculatus) actually damage the female’s reproductive tract during sex, and females, understandably, kick them for it. If she doesn’t kick, injuries tend to be worse after a longer sex session. Yet according to this paper, the carnage is not a deliberate act of destruction by the males, just an unfortunate by-product of them evolving weapons that are literally weapons. Why, it’s not yet known, but the theory is its all about being able to cling tightly to their ‘loved’ one.

If this blog puts insects in danger of being adopted by the alt-right as beacons of ultra- masculinity, hold that thought right there. Transgression of gender norms is happening in Brazilian caves, don’t you know. In the louse genus Neotrogla, it’s the females with the penis-like protrusion, and the guys with a chamber comparable to a vagina. A very niche re-definition of ‘wearing the trousers’ for sure, and in marked contrast to the species of beetles and dragonflies using their phallus to screw over their rivals with a bit of sperm scooping, our ‘macho’ cave-based females are using theirs to collect it up. Through all the kink and horror, life finds a way.

So there, a piece about insect nobs has been published on the Entomology MSc blog. I can only hope this comes up in the exams in March, making things a little less hard. Too much smut? Probably.

 

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An Update (Part 2)

Welcome back peeps! Here’s the second part of the overview/highlights of what we’ve been getting up to so far on the course:

Module 2: Diversity & Evolution of Insects

This module was a nice transition from the previous module content-wise. The first day was a mixed bag, it started with a lecture from Prof. Simon Leather (@EntoProf) on the history of entomology as a subject and insect paleontology (come on, who doesn’t love a bit of Meganeura spp.). Followed by Dr. Andy Cherrill giving a lecture on intraspecific variation. Theeeeen, back to Simon, with a lecture on the super weird, awe-inducing and ever so slightly ridiculous aphid life cycle. The day concluded with the first guest speaker for this module: Professor Tony Dixon! He gave us a lecture on aphid thermobiology and coccinellids (ladybirds, namely on generation time and their usage in biocontrol). He was Simon’s PhD supervisor! It was a privilege to be lectured by someone who has been in the game for so long, is still publishing research and has taught one of our lecturers. The next day was also a healthy mix of topics, covering soil biodiversity to aquatic insects and estimating insect species diversity.

Leading on from the previous day, we had a lecture on Acari (ticks and mites). The study of non-insect arthropods meshes nicely with entomology. As entomologists, it is important for us to be able to identify relatives and to understand their ecological interactions. The rest of the day was full of the mighty Odonata! Starting with a series of lectures from guest speaker Steve Brooks (once again, from NHM) on the identification of British Anisoptera (dragonflies) and Zygoptera (damselfies). The afternoon was spent gleefully identifying odonatans using their larval exuviae with The British Dragonfly Society’s Shropshire County Recorder, Sue Rees Evans!

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The larval exuviae of the Southern Hawker (Aeshna cyanea). Dragonfly larvae are predatory and possess a labial “mask”, a modified labium tipped with pincers. The mask is fired out to grab and immobilise prey. 

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The larval exuviae of a damselfly. The appendages on the rear are called lamellae and they aid gas exchange.

With Odonata checked off the list, we had a day dedicated to an assortment of insect orders with Dr. Mike Copeland. To name a few, we covered the Phasmida, Dermaptera and Neuroptera. The following day started off with a practical session in which we unleashed the fury of lacewing larvae onto some chubby mealybugs; a little taster of what is to come in the Commercial & Practical Biological Control module!

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A lacewing larvae chowing down on a mealy bug. They are voracious predators with specialised mandibles used to extract the bodily fluids of their prey.

The module and week ended on a mellow note, with another chill session of pinning and curation. Practice makes perfect!

Module 3: Experimental Design & Analysis

Being able to design an experiment to test a hypothesis and then analysing the acquired data using the appropriate statistical analyses, holds fundamental importance in science. Once again, the course is full of people with varying levels of experience in different areas, and statistics is no exception. The module reinforced the importance of a robust experimental design, and introduced the cohort to the statistical software R and how to run a range of tests using it. Of course, I would rather have fun practicals over this in a heartbeat, but you can’t replace bread and butter with more filling and expect to have a sandwich! Having just finished this module, we start the Commercial & Practical Biological Control module on Monday! *crowd cheers* HUZZA!!

Soooooo…that’s it from me for now! Linzi will be posting an article on Tuesday on insects which survive in extreme environments and their adaptations to the hostile conditions they live in.

Until next time!

 

By Aqib Ali  (Twitter:@EntoAqib , Email: Aqib1996@hotmail.co.uk , Linkedin: Aqib Ali)

MSc Entomology Twitter: @EntoMasters