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Guide to New Zealand's freshwater invertebrates
Purse caddis
(
Hydroptilidae
: Paroxyethira
)
Diagnostic features
Paroxyethira caddis larvae construct small, transparent, mobile cases shaped like a purse (hence the common name “purse caddis”). Each of the three thoracic segments has a hard (“sclerotised”) covering.
Typical habitats
Paroxyethira larvae are common in slow flowing, unshaded streams, particularly amongst weed beds or algal growths.
Feeding
They feed on filamentous algae.
Indicator value
Abundances of Paroxyethira larvae are usually recorded at sites with abundant streambed algae or weed beds. Such growths are likely to be the result of nutrient enrichment, limited shade and a lack of recent high flow (algae scouring) events. They have low tolerance values of 2 (hard bottom sites) and 3.7 (soft bottom sites).
