Measurement of the length of the first two antennal segments in Choerades
M. J. SMART*
[* The author sent this description to Mr. Geller-Grimm - not published]
A problem arieses in the measurement of the length L1 of segment 1 because the outer edge of segment 1 is not perpendicular to the long axis of the segment (in cross section the segment is trapezium-shaped)
It is therefore necessary to define L1 as either:
- the minimum length L1a
- the maximum length L1b or,
- the average of the two = (L1a+L1b)/2
Measurement of the antennal length
A second problem arises because the long axis of segment 2 is not aligned with the long axis of segment 1. Theoretically, L1 should be measured with the microscope graticule in one position and L2 with the graticule of a different angle, so that it is aligned with the long axis of each segment individually. In practice, any movement or adjustment of the microscope between measurements involves introducing baseline and/or parallax errors into the measurements. It is therefore better to make both measurements along the axis of segment 1 - i.e. as M1 and M2, but this will involve a slight underestimation of L2.
For the purposes of the present exercise, I have measured M2 and M1 assuming M1 = (L1a+L1b)/2.
The ratio L1/L2 has been assumed to be equal M1/M2.
Malcolm J. SMART, Southcliffe, Pattingham Road, Wolverhampton WV6 7HD, United Kingdom, firstname.lastname@example.org
Last saved Feb. 02 1998
© F. Geller-Grimm