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Why some insect eggs are spherical while others look like hot dogs

Look at the nail of your pinky finger. Thats about the width of the biggest known insect egg, which ..

Look at the nail of your pinky finger. Thats about the width of the biggest known insect egg, which belongs to the earth-borer beetle Bolboleaus hiaticollis. The smallest egg, from the wasp Platygaster vernalis, is only half the width of the thinnest recorded human hair.

Insect eggs range across eight orders of magnitude in size, and come in a stunning variety of shapes, a new database of almost 10,500 descriptions of eggs from about 6,700 insect species shows.The Harvard University team behind the database thinks its figured out one reason why. In a separate analysis, the researchers determined that where insects lay their eggs — for example, in water or in the bodies of other critters — helps to explain some of the diversity thats evolved over time. The database and study were both published July 3 in Scientific Data and Nature, respectively.

“Eggs provide a wonderful window into the evolutionary and ecological forces involved in animal reproduction,” says Mary Stoddard, an evolutionary biologist at Princeton University not involved in the new work. Stoddard and her colleagues analyzed over 47,000 photos of eggs of 1,400 bird species in a 2017 study, which found a link between a birds egg shape and the animal's ability to fly. “Compared with bird eggs, insect eggs are truly wild,” she says. “Some insect eggs are spherical or elliptical, but others resemble arrowheads or hot dogs.”

To compile the database of insect eggs, researchers developed computer programs that extracted egg measurements from text and photos in 1,756 digitized publications, and then used the measurements to estimate egg sizes and shapes. Representatives of over 500 families from all insect orders were included.

Harvard University evolutionary and developmental biologist Cassandra Extavour, an author of both papers, says that eggs, being just single cells without complex features that might complicate comparisons, make a “great starting point” to study how insects develop.

Analyzing the egg data revealed an astounding diversity. Still, within that variety, many insect groups have converged upon similar designs, such as spherical or elongated, says Samuel Church, an evolutionary biologist at Harvard University.

All sizes[hhmc]

These drawings represent the range of sizes found in insect eggs. The largest, from an earth borer beetle (left), is about 800 million times as big as the smallest egg, from a parasitoid wasp (right). An analysis of thousands of insect species eggs suggests larger eggs tend to be laid in soil or under leaf litter, while smaller ones are laid in water or within another animals body.

    <img src="https://www.sciencenews.org/sites/default/files/2019/07/061319_yao_insecteggs_inline1_370.png" title="~~ S. H. Church &lt;em&gt;et al&lt;/em&gt;/bioRxiv.org 2018 (&lt;a href=&quot;https://creativecommons.org/licenses/by/4.0/&quot;&gt;CC BY 4.0&lt;/a&gt;)" />  

Scientists previously had proposed reasons for those similarities; larger eggs, for example, might be more elongated because its easier for females to lay them. But using phylogenetic and statistical aRead More – Source
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