This 2017 video from France says about itself:
Microplitis retentus (Papp, 1984)(Hymenoptera : Ichneumonoidea : Braconidae) parasitizes a caterpillar of the Orange Tip, Anthocharis cardamines (Linnaeus, 1758) (Pieridae: Pierinae: Anthocharini)
This 5 mm long wasp parasitizes young caterpillars of the Orange Tip. Using its ovipositor, it injects a single egg in its victim. The parasitoid larva develops inside its host (endoparasitoid) where it lives off the haemolymph, without preventing the host’s growth. When the caterpillar becomes about 15 mm long it climbs high up on the food-plant, and after some time the parasitoid larva erupts above the 2nd and 3rd abdominal prolegs, and then it immediately spins a cocoon next to the caterpillar, which remains alive for a few days. After about 10 days the adult wasp bites a clean circular lid from the end of the cocoon, most of the time at the underside of its cocoon, allowing it to emerge.
In the rearing shown here, the wasp emerged from its cocoon quite rapidly, and there is then a further generation, overwintering in the cocoon. However, it may be more usual for there to be only one generation, with harder and darker cocoons that withstand not only the rest of the summer but also the winter.
Remarks and identification Dr. Mark R. Shaw
And now, relatives of this parasitic wasp species, discovered dar from France.
Date: July 3, 2019
Summary: Specimens kept in the collection of the Institute of Beneficial Insects at the Fujian Agriculture and Forestry University (China) revealed the existence of two previously unknown species of endoparasitic wasps. Looking very similar to each other, yet clearly distinct from species in other wasp genera, both have once been collected from prairies and bushes in high-altitude areas in Tibet, China.
Specimens kept in the collection of the Institute of Beneficial Insects at the Fujian Agriculture and Forestry University (FAFU, China) revealed the existence of two previously unknown species of endoparasitoid wasps. Originally collected in 2013, the insects are known to inhabit prairies and bushes at above 3,400 m, which is quite an unusual altitude for this group of wasps.
The new to science wasps are described and illustrated in a paper published in the open-access, peer-reviewed scholarly journal ZooKeys by the team of Dr Wangzhen Zhang (FAFU and Fuzhou Airport Inspection and Quarantine Bureau) and his colleagues at FAFU: Dr Dongbao Song and Prof Jiahua Chen.
Looking very similar to each other, the species were found to belong to one and the same genus (Microplitis), which, however, is clearly distinct from any other within the subfamily, called Microgastrinae. The latter group comprises tiny, mostly black or brown wasps that develop in the larvae of specific moths or butterflies. Interestingly, once parasitised, the host continues living and does not even terminate its own growth. It is only killed when the wasp eggs hatch and feed on its organs and body fluids before spinning cocoons.
From now on, the newly described wasps will be called by the scientific names Microplitis paizhensis and Microplitis bomiensis, where their species names refer to the localities from where they were originally collected: Paizhen town and Bomi county, respectively.
Due to their parasitism, some microgastrine wasps are considered important pest biocontrol agents. Unfortunately, the hosts of the newly described species remain unknown.
In addition, the scientists also mention a third new to science species spotted amongst the specimens they studied. However, so far they have only found its male, whereas a reliable description of a new microgastrine wasp requires the presence of a female.