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We're kicking off July with a beautiful butterfly that does horrible things to ants!\n\nFurther reading:\n\nUK Butterflies - Large Blue\n\nThe large blue butterfly (picture taken from page linked above):\n\n\n\nShow transcript:\n\nWelcome to Strange Animals Podcast. I\u2019m your host, Kate Shaw.\n\nI recently realized that I have so many weird and interesting invertebrates saved up to feature for invertebrate August that I can\u2019t fit them all into one month, so let\u2019s kick off invertebrate August in July!\n\nThis week we\u2019re going to learn about a beautiful butterfly called the large blue, because it is both large and blue. Well, sort of large. The butterfly has a wingspan of up to two inches, or about 5 cm. Its wings are a dusty blue with black spots, although there are a lot of regional differences. Some populations are almost black, some are more tan than blue, and some don\u2019t have spots.\n\nThe large blue lives throughout much of Eurasia, although its numbers have decreased in many places in the last 50 years or so. In some places it\u2019s even gone extinct, mainly due to habitat loss. It needs specific host plants for the caterpillars to eat, and it also needs a particular type of ant in order for the caterpillars to survive--because the large blue caterpillar is a brood parasite!\n\nWe\u2019ve talked about brood parasites before in birds, where a bird will lay an egg in the nest of a different species of bird. In the case of the large blue butterfly, in summertime the female lays her eggs on wild thyme or marjoram plants near a colony of red ants in the genus Myrmica [meer-mee-kuh]. She usually only lays one egg on any given plant.\n\nWhen the eggs hatch, the newly emerged caterpillars feed on plants at first, just like any other caterpillar, especially the flowers of the plant. If more than one large blue caterpillar is on a plant and they encounter each other, one of them will grab the other and eat it. Drama among the thyme plants! The caterpillar goes through three growth stages, called instars, as an ordinary caterpillar (except for the cannibalism thing), but once it reaches the fourth instar it starts acting very different.\n\nThe caterpillar drops to the ground and releases a chemical that mimics the smell of the Myrmica ant larvae. When an ant finds a caterpillar, the caterpillar will rear up so that it resembles an ant larva. The ant usually takes it back to its nest at this point, but sometimes the caterpillar will just follow an ant trail and enter the nest on its own. Either way, the ants will assume it\u2019s a lost baby and take it to the nesting chamber, where they feed and take care of it.\n\nThe caterpillar is bigger than a usual ant larva, but it uses this to its advantage. It mimics the sounds made by a queen ant, which means the ants take extra good care of it. If the ants run out of regular food to feed the caterpillar, they will even start feeding it real ant larvae. But sometimes the caterpillar gets impatient, or maybe just hungry, and will just start eating the other pupating ant larvae.\n\nThe system isn\u2019t perfect, because a lot of times the ants figure out that the caterpillar is an intruder and will kill and eat it. If the queen ant encounters the caterpillar, she recognizes that it isn\u2019t an ant larva and will attack it. Sometimes the ants just up and abandon the nest, leaving the caterpillar behind. In that case, the caterpillar will either leave the nest itself and find another one, or it will wait for a new ant colony to find the nest and move in. This can actually happen repeatedly during the nine months or so that the caterpillar requires to finish growing, although during the winter the caterpillar is more or less dormant.\n\nAround the end of spring, the caterpillar spins a cocoon and pupates right there in the ant nest. The ants continue to take care of it, making sure the pupa is clean. When it emerges as a new butterfly after a few weeks, it has to find its way out of the ant nest and to the surface,