A key aspect of modeling contaminant uptake by animals is knowledge of the route taken by the contaminant to enter the animal. To determine the relative importance of food and water as Cd sources for benthic insects, we measured Cd accumulation by the predatory alderfly Sialis velata (Megaloptera) from either water alone or from chironomid prey (Cryptochironomus sp.). We determined that Cd uptake from prey was far more important than that from water. Chironomid prey fed to S. velata also appeared to take up the bulk of their Cd from food (meiobenthic organisms). The efficiency with which Cd was assimilated by the predator from its prey is high (50%) and comparable with values reported for several other insects. In the predator, Cd taken up from food was largely stored in gut tissues (as is the case for insect larvae in nature), whereas a greater proportion of the metal taken up from water was stored in other animal parts.

1. Colonies of the social caterpillar Eutachyptera psidii (Sallé) (Hymenoptera: Lasiocampidae) occurring on oak (Quercus) in upland forests of Mexico endure periods as long as 6 weeks, with little or no food or water between the time host trees shed their leaves in April and produce new leaves in June. 2. By monitoring the activity of both field and laboratory colonies with infrared activity monitors and data loggers, it was found that although colonies remain active during the period of deprivation, their foraging activity shifts from once nightly when food is available to once every second night when food-deprived. 3. Over a period of absolute food and water deprivation of 18 days, caterpillars lost an average of 36% of their initial mass but none perished. On average, the caterpillars regained their pre-starvation mass within a few days after food was provided and continued to grow thereafter. During the period of starvation, caterpillars were observed to chew on dead and dried leaves in the field and on sheets of paper in the laboratory. 4. To the authors' knowledge, there is no other documented instance of a species of caterpillar that exhibits the physiological capacity to engage in a similar level of persistent activity when forced to endure a prolonged period with neither food nor water.