I am completely under so much pressure to get so many things done before the hearing (hopefully it will all be worth it and good things shall ensue, and by the way, you are preparing your testimony too, right? right?), so I humbly offer you a wee bit more Johnson from my obsessive reading for your enjoyment.

The paper in question:
Johnson, C. G. 1941. The ecology of the bed-bug, Cimex lectularius L., in Britain. Journal of Hygiene 41: 345–461

Our last post:
Johnson’s hut

How often do bed bugs go out and forage for food? In the presence or absence of a host? I think we still don’t really know, but Johnson of course tried to figure it out.

He marked bed bugs with paint on the thorax (a separate test confirmed the amounts of paint used were not toxic). Nine distinct colors were used to represent numbers 1 to 9:

Then by putting two spots side by side a number such as 23 or 12 could be written. Thus three spots side by side gave a number of, for example, 223 or 488.

Then he could determine how often the same bed bug was trapped in an experiment that lasted 113 days with fasting bed bugs.

Number of times bed bugs were trapped:

1 capture – 32 adult males, 15 adult females
2 captures – 18 males; 12 females
3 captures – 10 males; 16 females
4 captures – 4 males; 7 females
5 captures – 3 males; 11 females
6 captures – 1 male; 6 females
7 captures – 4 males; 6 females
8 captures – 1 male; 4 females
9 captures – 2 females
10 captures – 1 female
11 captures – 1 female
12 captures – none
13 captures – 1 female

He determined the mean period between trappings was 48.3 days for males and 27.9 days for females (at a mean temperature of 18.7dC).

Because “practically no activity occurred for the first 36 days” (which is interesting, isn’t it? in the absence of a host, they may stay quietly where they are for a while), he adjusted accordingly and came up with a mean period between trappings of 32.9 days for males and 19.0 days for females (at a mean temperature of 19.7dC).

So, females were definitely more active, out there walking about more often than males.

Of course, average periods! He notes that the frequency was greater sometimes, naturally:

the same females were often caught three or four nights in succession.

And, he was circumspect (this is absolutely great about reading Johnson in general, his reluctance to make grand claims and his insistence on the inadequacy of what could be determined):

The actual frequency with which bugs emerge is, however, unknown: the above figures indicate minimum rather than actual values. Little is known, either, about the frequency with which bugs feed if a host is always accessible. But Mellanby (1939b), by the use of indirect methods, estimates that the males in the population he studied fed at 4-8 day intervals and the females at about 5-day intervals. The temperature was not stated precisely but fluctuated between 20 and 27 [degrees] C. (68.0 and 80.6 [degrees] F.). In other infestations with a human host (Mellanby’s room was full of caged rats) and with lower temperatures the frequency might well be considerably less than this.

The reference to Mellanby here is: Mellanby, K. (1939) The physiology and activity of the bed-bug (Cimex lectularius L.) in a natural infestation. Parasitology, 31(2), 200-11. (Sorry, I don’t have this one.)

Do you like these Johnson posts? Because obviously I can go on and on. Or not. Drop me a note. Sorry, there is nowhere you can download this paper. I went to the library and got dead-tree copies.