{"id":1,"date":"2015-09-16T18:07:29","date_gmt":"2015-09-16T18:07:29","guid":{"rendered":"https:\/\/zeppmusic.com\/Arthroblog\/?p=1"},"modified":"2015-09-23T13:11:27","modified_gmt":"2015-09-23T13:11:27","slug":"manduca","status":"publish","type":"post","link":"https:\/\/zeppmusic.com\/Arthroblog\/2015\/09\/16\/manduca\/","title":{"rendered":"The Wonderful World of Parasitoids"},"content":{"rendered":"

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Most people who have ever tried to grow tomatoes have certainly run into hornworms. These caterpillars are the larvae of hawk moths. \u00a0Strangely enough, the hornworm most commonly found on tomatoes is not<\/em> the tomato hornworm<\/strong>, Manduca quinquemaculatus<\/em> (Haworth), but the tobacco hornworm<\/strong>, M. sexta<\/em> (L.).\"manduca_larva\"<\/p>\n

As common and large as this pest is, many people never see (or never know they’ve seen) the adult moths. \u00a0They are nocturnal\u00a0and do their very best to look like tree bark when resting during the day.\"manduca_sexta_adult\"<\/a><\/p>\n

Tobacco hornworm larvae can get rather large: the size of an adult’s finger is not unusual. \u00a0Owing to their great camouflage,\u00a0people ofter don’t even see these gigantic critters on their plants until they notice a lot of missing leaves, or they see the suddenly obvious caterpillars looking like this:<\/p>\n

\"Parasitic-wasp-eggs-on-hornworm1\"<\/a><\/p>\n

So what are those cute little white tufts? \u00a0No, they are not decorations the caterpillar has chosen, they are cocoons. \u00a0Each cocoon has been spun by a tiny Cotesia<\/em> congregata<\/em> wasp larva which hatched from an\u00a0\u00a0egg laid inside this rather unfortunate hornworm. \u00a0The hundreds of eggs in each caterpillar hatch in a few days and the larvae then feed on the caterpillar from the inside for a couple of weeks, causing its ultimate demise.<\/p>\n

This killing of the host, BTW, is the difference between a parasite<\/strong> and a parasitoid<\/strong>: a parasite feeds on another organism but does not usually threaten the host’s existence (think fleas or lice–annoying, but not inherently deadly). \u00a0Conversely, a parasitoid feeds on its host, and in so doing, kills it–this is the case with these tiny wasps.<\/p>\n

In a move straight from Alien<\/em>, the mature larvae chew their way out of the caterpillar, through its integument (“skin”), which brings us to the photo and video I took on 15 Sep 2015 when I found this caterpillar on our tomatoes. \u00a0In the photo, we can see:<\/p>\n