Some tachinids can be difficult to identify and need careful examination to reach a species. Most are similar in shape to house flies but they tend to be very bristly and often quite dull in colouration, although some species are quite bright and well marked. The larvae are internal parasites of caterpillars, shieldbugs and some other insect families, the eggs being laid inside, on or close to the host and the larvae making its own way inside, or onto the food plant so that the host species ingests them. They then eat the host from within, leaving the essential organs until last. When they are ready to pupate they kill their host.