Producer: Popular Science China
Producer: Ge Qingsong, Qiu Xi (Ribose Apartment), Yang Mei (Kunming Institute of Botany, Chinese Academy of Sciences)
Producer: Computer Network Information Center, Chinese Academy of Sciences
Do you think these are the fruits of some kind of plant?
Image credit: Flickr
If you answer "yes," then you are deceived!
I don't want to tell you that I was once a liar: on a business trip I saw the "fruit" of Quercus aliena var.acutiserrata (bottom left), but it was supposed to look different (bottom right), was it the wrong way I opened it?
Image source: Shangguan Fazhi
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△ Video source: https://v.qq.com/x/page/r3077rydeps.html
Sharp-toothed quercus quercus "fruit" section of the gall bee larvae Image source: Shangguan Fazhi
Some kind of angusic bee andricus drilled out of the "fruit" Image source: Shangguan Fazhi
It turns out that these "fruits" are all camouflaged by gall bee galls!
"Gall" refers to the nodular protrusion formed by the plant after being stimulated by the outside world, and the word "worm" refers to the gall-causing insect, that is, the creator of the gall. Insects use chemical or physical stimulation during spawning and feeding to accelerate plant cells growth, abnormal differentiation, and finally the formation of hard insect galls. Galls are common in the wild, mostly manifesting as small protrusions on the leaves, small tumors, irregular spots, etc.
Different types of gall Image source: Flickr & Shangguan Fazhi
The parasitic behavior of small insects is very common, and the process is simple and rough, either directly attaching to other animals or eating deeply into the plant. And "vegetarian" behaviors like gall bees that parasitize plant tissues are rare. In addition to the aforementioned Cynipidae, "vegetarian" parasites include small insects from taxa such as the globulus cecidomyiidae, Pemphigidae, and Thripidae. The plant species and parts parasitized by each insect are different, from coniferous to broad-leaved, herbaceous to woody, leaves to young stems, can find traces of galls. But most of the time, a gall-causing insect only glides on specific parts of a plant, so galls can be used to identify certain types of plants and parasitic insects, such as the aforementioned sharp-toothed quercus quercus, which has a stable association with small flying insects of the genus Angona.
The picture on the left is the gall bee, the right picture is the bee Image source: Marc Kummel, flickr .and wikipedia.
Among the various gall-causing insects, the gall bee is the most successful gall-causing insect, almost winning the insect gall world creativity award. It built a variety of specially shaped and structurally complex galls, developing unique jumping behaviors and efficient reproductive strategies. Its number of species has evolved into more than a thousand species, resulting in a large family with extremely high diversity.
The gall form "created" by the gall bee is the most complex and subtle. From the outside, the gall house of the gall bee is generally spherical, thorny, rhomboid, etc., and some even resemble some kind of fruit. Breaking open the gall wall, the outermost layer of plant tissue thickens and hardens, protecting the larvae in it, the cells in the inner layer are soft and nutritious, and the middle cavity mansion is inhabited by fragile gall bee larvae. The survival advantages of this structure are obvious: both to insulate the larvae from external environmental influences and to avoid predator attacks, the larvae will safely hide in the gall and eat the plant tissue and slowly grow.
Image source: literature: Galls and gall-causing insects
Image source: Reference 6
North America is home to the world's most diverse oak forest, known locally as quercus garryana, a host plant for the famous Neuroterus saltatorius. The larvae of this gall bee live quietly in the gall on weekdays and are nothing special compared to other galls. But in the summer, the galls on the leaves become restless, falling off and densely packed. The galls that fell to the ground immediately jumped up non-stop, and although each gall was only 1 millimeter in size, it could jump aimlessly for several days with a jumping power of 3 centimeters. It's hard not to get noticed by this unique jumping behavior, which locals call Jumping Gall Wasps. But the seemingly blind behavior reflects the unique survival wisdom of the gall bee - because as long as it keeps jumping, it is likely to end up falling into the stone crevice or fallen leaves, and there is not only a stable low temperature and high humidity environment, but also to avoid the threat of other parasitic bees. So the larvae with the gall settle down, pupate overwinter, and when spring comes, it bites through the gall wall and begins another generation.
Image credit: MEETGAB and Featured Creatures.
However, the most amazing survival strategy of gall wasps is not the structure and jumping behavior of galls, but a form of reproduction known as periodic parthenogenesis. This method of reproduction is not uncommon in insects, which win by the number of offspring, aphids are well-known unisexual reproductive strategy insects, most of their reproductive behavior throughout the year is parthenogenesis, do not need to mate; only in the late summer of environmental changes, only a sexual reproduction, produce more adaptable offspring, to survive the long cold winter. The parthenogenous reproductive strategy of gall wasps is more efficient and has a strict periodicity. Most gall bees reproduce only for two generations, one sexual and one unisexual. In early spring, when the temperature rises, the overwintering gall wasps bite through the gall wall and feather out, the male and female mate for sexual reproduction, and the unfertilized eggs develop into haploid males after mating, and the fertilized eggs develop into diploid females. The offspring produced by the first generation will be feathered in the summer and undergo unisexual reproduction, with all offspring being females and not requiring mating and fertilization to lay eggs. Because they do not need to mate with males, female bees of some species even have their wings degraded, saving energy while increasing the number of eggs and maximizing the benefits of reproduction.
The picture on the left shows the morphology of the sexually reproducing gall, and the picture on the right shows the form of the asexual breeding gall Image source: Featured Creatures.
Although the gall bee is a mild vegetarian in the family of parasitic bees, it does not draw a line with its relatives, but connects with them through parasitism. Widely distributed in the southeastern United States, there is a bassettia pallida that parasitizes on the delicate stems of the Quercus virginiana and quercus geminata trees, and the larvae build multiple luxury apartments (galls) next to each other, forming inconspicuous lumps and cultivating obscure spots in the gall house. As their natural enemy, the Euderus set, which is also a parasitic wasp, does not rely on vision to find galls, but quickly taps its tentacles, follows the smell to find the location where the galls gather, erects sharp and slender laying tubes to puncture the galls, and precisely lays the eggs in the body of the gall bee larvae. After hatching, the larvae of the ji bee carefully feed inside the gall bee larvae, never harming the key organs so as not to kill the host. The larvae of the gall bee would have successfully pupated, feathered, and then bit a hole in the gall wall that was larger than the width of the body and flew to the outside world. But then it couldn't do it, and the parasitic Ji Wasp would signal that it would stop when the opening of the cave was not wide enough, like a cork on a wine bottle, and block the hole with its head. The gall bee larvae then stopped moving and slowly died, and the wasp finally ate the host's body, and then bit through the host's head, flying away from the hole the host had dug for it.
Image credit: Pinterest.
This set of exquisite and complex parasitic behaviors is actually compatible with its body structure, Ji Xiao bee is too small, the mouth organ is not as developed as the gall bee, can not bite the hard gall, had to drive the host to work for himself, bite open the narrow window to prepare for future feathering, so as not to be trapped in it.
Image source: Reference 4
The "success" strategy of the gall bee is just the tip of the iceberg for the many complex survival behaviors of insects. In the world of insects, there are many more interesting phenomena waiting to be paid attention to, and even the gall itself still has many mysteries to be solved: what substances are the larvae through that can so directly affect the differentiation and mutation of plant tissues? There are many gall forms, what are their functions and significance? Everything is waiting for us to discover and explore further!
Resources:
[1] Graham N. Stone1&James M. Cook. The Structure of Cynipid Oak Galls：patterns in the evolution of an extended phenotype[J]. 1998 The Royal Society.
[2] Saige Manier & David Deamer. Jumping Galls：a Novel Mechanism for Motility[J]. Insect Behav DOI 10.1007.
[3] Peter W. Price et al. Hypotheses On The Adaptive Nature Of Galls[J]. PROC. ENTOMOL. SOC. WASH. 88(2), 1986.
[4] Anna K. G. Ward et al. A keeper of many crypts：a behaviour-manipulating parasite attacks a taxonomically diverse array of oak gall wasp species.
[5] Graham N. Stone & Karsten Scho¨ nrogge. The adaptive significance of insect gall morphology[J]. TRENDS in Ecology and Evolution Vol.18 No.10 October 2003.
[6] Graham N. Stone, Karsten Schonrogge et al. the population biology of oak gall wasps (hymenoptera: cynipidae)[J]. Annu. Rev. Entomol. 2002. 47.
[7] Wang Guangyu, Wang Yiping, Wu Hong. Galls and gall-causing insects[J].Insect Knowledge,2010,47(2).
The article only represents the views of the author and does not represent the position of the China Science Expo