Data from: Inferring the feeding history of the castor bean tick, Ixodes ricinus from lipid and body measurements

The ability to determine when ticks last fed and assign them to a specific
feeding cohort is important in attempts to explain their population
dynamics; the biochemical measurement of stored lipid, has been widely
used for this purpose. However, when relating feeding history to behaviour
or infection status, a non-destructive approach to its assessment would be
of value and, to this end, previous studies have attempted to use
morphometric indices. Within any instar, the sclerotised scutal components
of the body will not vary with increasing starvation while the alloscutal
components will, and the resulting ratio should provide a measure of time
since feeding. Here, the aim was to determine whether such a morphological
ratio (described here as the hunger index) changed predictably with
starvation in Ixodes ricinus L. (Ixodida: Ixodidae). For this a cohort of
300 I. ricinus nymphs was collected from the field in February 2021 and
starved in a humidified incubator at 15°C and 80% relative humidity (RH).
Every 2 weeks, 50 nymphs selected at random were removed and killed by
freezing; morphometric measurement was followed by the measurement of
lipid using a standard spectrophotometric approach. Both hunger index and
stored lipid changed significantly with increasing starvation and were
positively correlated with each other. However, the change in morphometric
ratio was relatively slight (11%) over 9 weeks and the variation was high.
The data suggest therefore that morphological measurements could be used
to provide, at best, only broad categorisation of the hunger status of
individual I. ricinus ticks in the field.