Strepsiptera – the weirdest insect eyes
Strepsiptera are some of the world’s weirdest insects. 1
"The eyes of strepsipteran insects are very unusual among living insects. In their anatomical organization they may form a modern counterpart to the structural plan proposed for the eyes of some trilobites. Externally they differ from the usual “insect plan” by presenting far fewer but much larger lenses. Beneath each lens is its own independent retina. Anatomical and optical measurements indicate that each of these units is image-forming, so that the visual field is subdivided into and represented by “chunks,” unlike the conventional insect compound eye that decomposes the visual image in a pointwise manner. This results in profound changes in the neural centers for vision and implies major evolutionary changes." 2
"No other insect that we know of has eyes quite like this," said Ron Hoy, professor of neurobiology and behavior at Cornell and co-author, with Cornell postdoctoral associates Elke Buschbeck and Birgit Ehmer, of the Science report. "The only place one may see a comparable eye structure is in the fossils of some kinds of trilobites," he says, referring to the extinct arthropods that lived in shallow seas during the Paleozoic era. 3
They look weird, they act weird and, like many parasites, they have a very weird life-cycle. Over 600 species have been described and they are all parasitoids, attacking insects from seven different orders – silverfish, flies, crickets, wasps… A parasitoid is an organism that lays its eggs inside another organism, often, but not always, with catastrophic effects for the host. Strepsiptera seem to be an exception, for the host is generally able to survive rearing alien offspring within their bodies – in this sense strepsipterans are closer to parasites than parasitoids.
There is a huge dimorphism between the two sexes. The tiny males (2 mm long) are free-flying with odd, forwardly-curved, twisted wings (hence the name Strepsi-ptera). Once they hatch from their pupa (Strepsiptera are holometabolous, that is, they have a full metamorphosis), males live for only a few hours, and have only one job in life: to find a mate.
In flies, as we have discussed a number of times, the rear pair of wings are reduced to form halteres or balancers, which aid in flight. In Strepsiptera, the same process has taken place but it has involved the front pair of wings. How does this affect how the male flies? Do they have exactly the same function as in flies?
They also have weird branched antennae, odd globular eyes and vicious scissor-like mandibles. Check it out – have you ever seen anything like it? What do the males use those mandibles for? Can you guess (answer below)?
Although these eyes look weird, they are similar to some nymphs in hemimetabolous insects (that is, those insects that do not have full metamorphosis but instead have a series of moults). Intriguingly, male larval Strepsiptera also develop wing buds, like some hemimetabolous nymphs.
1. https://whyevolutionistrue.com/2015/12/02/strepsiptera-the-weirdest-insects/
2. http://www.thefossilforum.com/index.php?/topic/61411-modern-insect-with-trilobite-like-eyes/
3. https://news.cornell.edu/stories/1999/11/novel-insect-eye-could-be-old-way-seeing
Strepsiptera are some of the world’s weirdest insects. 1
"The eyes of strepsipteran insects are very unusual among living insects. In their anatomical organization they may form a modern counterpart to the structural plan proposed for the eyes of some trilobites. Externally they differ from the usual “insect plan” by presenting far fewer but much larger lenses. Beneath each lens is its own independent retina. Anatomical and optical measurements indicate that each of these units is image-forming, so that the visual field is subdivided into and represented by “chunks,” unlike the conventional insect compound eye that decomposes the visual image in a pointwise manner. This results in profound changes in the neural centers for vision and implies major evolutionary changes." 2
"No other insect that we know of has eyes quite like this," said Ron Hoy, professor of neurobiology and behavior at Cornell and co-author, with Cornell postdoctoral associates Elke Buschbeck and Birgit Ehmer, of the Science report. "The only place one may see a comparable eye structure is in the fossils of some kinds of trilobites," he says, referring to the extinct arthropods that lived in shallow seas during the Paleozoic era. 3
They look weird, they act weird and, like many parasites, they have a very weird life-cycle. Over 600 species have been described and they are all parasitoids, attacking insects from seven different orders – silverfish, flies, crickets, wasps… A parasitoid is an organism that lays its eggs inside another organism, often, but not always, with catastrophic effects for the host. Strepsiptera seem to be an exception, for the host is generally able to survive rearing alien offspring within their bodies – in this sense strepsipterans are closer to parasites than parasitoids.
There is a huge dimorphism between the two sexes. The tiny males (2 mm long) are free-flying with odd, forwardly-curved, twisted wings (hence the name Strepsi-ptera). Once they hatch from their pupa (Strepsiptera are holometabolous, that is, they have a full metamorphosis), males live for only a few hours, and have only one job in life: to find a mate.
In flies, as we have discussed a number of times, the rear pair of wings are reduced to form halteres or balancers, which aid in flight. In Strepsiptera, the same process has taken place but it has involved the front pair of wings. How does this affect how the male flies? Do they have exactly the same function as in flies?
They also have weird branched antennae, odd globular eyes and vicious scissor-like mandibles. Check it out – have you ever seen anything like it? What do the males use those mandibles for? Can you guess (answer below)?
Although these eyes look weird, they are similar to some nymphs in hemimetabolous insects (that is, those insects that do not have full metamorphosis but instead have a series of moults). Intriguingly, male larval Strepsiptera also develop wing buds, like some hemimetabolous nymphs.
1. https://whyevolutionistrue.com/2015/12/02/strepsiptera-the-weirdest-insects/
2. http://www.thefossilforum.com/index.php?/topic/61411-modern-insect-with-trilobite-like-eyes/
3. https://news.cornell.edu/stories/1999/11/novel-insect-eye-could-be-old-way-seeing
