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C18

Link: linnaeus.c18.net/Letter/L5945 • Ernst Friedrich Burchard to Carl Linnaeus, 27 September 1747 n.s.
Dated 1747. Sept. 27.. Sent from Rostock (Germany) to Uppsala (Sweden). Written in Latin.

upSUMMARY

Ernst Friedrich BurchardBurchard, Ernst Friedrich
(1724-1749). German. Doctor of
medicine, Rostock. Correspondent of
Linnaeus.
has felt encouraged by Linnaeus to study Coccus purpureus radicum, and after three months’ work, Burchard is ready to make a report which he sends to Linnaeus, with the usual caveat at the beginning that some facts may be misunderstood or incomplete.

Burchard has distinguished two species of the animal, one more common, one mainly confined to the region of Mecklenburg. He first describes the more usual one.

The insect is very common in most of Europe but less so in Sweden, as Linnaeus has observed. It is extremely common in Mecklenburg, where it occurs mainly on the roots of Scleranthus, but not everywhere. It is never found in cultivated fields but at their borders, and more often in sandy soil than in black. They are found in greatest number around midsummer, but Burchard had seen them both before and after, and they come later after a cold spring.

Burchard makes several observations on the relation between the plant and the insect, but these usually lead to open questions. However, Burchard describes in quite a lot of detail the eggs found on the plant, in which larvae of the insects are found, and what these eggs look like in different situations, what colour they have and how they smell.

From an egg that swells and turns pale, Burchard has seen a worm emerging, head first. In his samples, Burchard had seen many die in that phase, but when he had started to wet the sand around the eggs, more survived, and they escaped faster. They usually emerge at midday, not in the morning or in the evening. Burchard describes them in great detail: a head with two antennas and no eyes, and a body with twelve segments, three of which Burchard calls the body, the nine others the tail. Between the segments small hairs protrude, acting as legs.

All these anatomical observations have to be made under a microscope and with a very sharp knife. Burchard has made the description mainly from female worms, of which he has the greatest number. He has observed some difference in the shape of the body (the males are slimmer) and in their behaviour (the males are more agile, climb plants etc., while the females are heavier and less mobile).

However, Burchard had also observed them moving around, and made experiments on feeding them. He had not found that they eat anything but Scleranthus, but they could live for very long without eating anything at all.

After some weeks, the worms get covered in fluff, and they become less agile. After a final change of skin, the insect enters the chrysalis phase, which takes more than twelve days until the latter part of the month of July. After that, a fly appears, very laboriously.

The fly is red but becomes darker with time. Burchard also describes that in great detail. For example, Burchard observes that its two wings are large enough for such a small fly and that they are folded in three parts when the fly emerges from the chrysalis.

Burchard has rather little to tell on the life of the fly. It is very active and alert on the day after its incubation, but to his regret, Burchard has not been able to see how they manage to mate. However, he has seen that they return after some hours from that process, exhausted and with drooping antennas, after which they die. The total life of the fly is 24 to 28 hours.

However, Burchard had observed that some of the female worms did not develop like the others but continued, partly under ground, and that they were still alive at the beginning of October. He wonders what that can be, and leaves that issue to others.

Burchard then describes in briefhow the other variant of the insect differs from the more common one. They are smaller, with a brighter colour.

Several delineations illustrate the text of the description.