Manual for Diagnosis of Screw-worm Fly - xcs consulting

Cochliomyia macellaria
Agriculture, Fisheries and Forestry - Australia
Young females of C. macellaria generally have cuticular hydrocarbons of shorter chain length
than Co. hominivorax with alkanes of chain length 27 (particularly i-methylheptacosane) being
dominant. Also present are substantial quantities of n-nonacosane and i-methylnonacosane.
Data for males and for older flies are not available.
Distinguishing features for C. bezziana cuticular
hydrocarbons (Fig. 32)
Because of changes in cuticular hydrocarbon composition due to age, sex and probably
geographic source, for reliable species identification it is best to consider the cuticular
hydrocarbon pattern as a whole rather than to rely on one or two components. Thus cuticular
hydrocarbon values for a supposed C. bezziana should match reasonably well with the
values given in the Table and the traces in Fig. 32 for most if not all major components.
However, allowance for changes in cuticluar hydrocarbon composition with age should be
made using the values and the table as a yardstick. Since these values represent the limits
for each component, flies of intermediate age should have intermediate hydrocarbon values.
Culicular hydrocarbon changes cease with death so storage of a dead fly will not produce
any further change in hydrocarbon composition.
In spite of the cautionary note above, the following comments can be made: young
C. megacephala, C. saffranea and Co. macellaria generally have shorter chain length
hydrocarbons than does C. bezziana. Heptacosanes, especially i-methylheptacosane, are far
more abundant than in C. bezziana, whereas hydrocarbons of chain length greater than 30
are much more abundant in the latter. In view of the changes with age for the cuticular
hydrocarbons of C. bezziana and Co. hominivorax, it is likely that similar changes occur with
these other species, however, it is unlikely that these would be such as to cause older flies of
these species to mimic C. bezziana.
Newly emerged Co. hominivorax flies contain cuticular hydrocarbons dominated by
nonacosanes which are only relatively minor components of C. bezziana and lack the longer
chain material present in the latter. Older male Co. hominivorax flies develop large quantities
of pentacosanes and heptacosanes which are absent or at low levels in C. bezziana. Older
females of Co. hominivorax do develop some longer chain alkanes but not to the extent that
C. bezziana does. They also have much more i-methylheptacosane and n-nonacosane but
less 2-methyltriacontane than does C. bezziana.
The single most diagnostic component of the cuticular hydrocarbons of C. bezziana is
2-methyltriacontane, which is a major component in young and old males and females but is
present at only low levels in the other species. Similarly i-methyltritriacontane is present in all
stages of C. bezziana but occurs elsewhere only in old Co. hominivorax females.
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