Phylloneta impressa

(L. Koch, 1881)

Forest Cobweb Weaver

Phylloneta impressa is a small comb-footed spider (Theridiidae) with a Holarctic distribution. Males measure 2.5–5.5 mm and females 3.5–5.5 mm. The constructs tangle webs beneath retreats on vegetation and has been documented in agricultural settings including rape fields. It is closely related to and frequently confused with Phylloneta sisyphia.

Phylloneta impressa by (c) gailhampshire, some rights reserved (CC BY). Used under a CC-BY license.

Phylloneta impressa by Gergin Blagoev. Used under a CC0 license.

Theridion impressum M frei Araneae fg02 by Fritz Geller-Grimm. Used under a CC BY-SA 2.5 license.

Pronunciation

How to pronounce Phylloneta impressa: /ˌfɪloʊˈniːtə ɪmˈprɛsə/

These audio files are automatically generated. While they are not always 100% accurate, they are a good starting point.

Identification

Distinguished from the very similar Phylloneta sisyphia by : males peak in June–July and females in July–August, occurring slightly later than P. sisyphia. sac production in August–September also occurs later than in P. sisyphia. Both may co-occur on gorse, heather, and thorny bushes.

Images

Habitat

Vegetated including gorse, heather, and thorny bushes. Also recorded from rush florets in upper saltmarsh zones and from agricultural landscapes including rape (canola) fields. Constructs retreats on vegetation with associated tangle webs below.

Distribution

Holarctic distribution: widespread in western Europe (absent from Iceland), common in south and central England becoming scarcer north and west. Recorded across North America, Europe, Turkey, Caucasus, Russia (European to Far East), Kazakhstan, Iran, Central Asia, China, India, Romania, and Alaska (USA).

Seasonality

males recorded May–August, peaking June–July. Adult females recorded June–October, with one exceptional December record, peaking July–August. Juveniles emerge from sacs and are orally fed by females.

Life Cycle

Females produce a single spherical blue-green sac in August–September, retained within the retreat. Juveniles emerge and are fed orally by the female. males have been observed mate-guarding females in retreats.

Behavior

Constructs a retreat on vegetation with a characteristic tangle web suspended below, typical of Theridiidae. males engage in mate-guarding of females within retreats. Juveniles receive oral feeding from females after from sacs.

Human Relevance

Documented as accumulating residues in agricultural landscapes; 23 pesticide compounds detected in field-collected specimens from rape fields, including neonicotinoids (clothianidin, thiamethoxam, acetamiprid, thiacloprid, imidacloprid) and chlormequat. Serves as an indicator of pesticide exposure in agroecosystems.

Similar Taxa

Phylloneta sisyphiaVery similar in appearance and use; distinguished by earlier ( and sacs peak earlier in the season) and minor pattern differences

More Details

Pesticide bioaccumulation

Study detected 23 compounds in P. impressa females, cocoons, and webs from rape fields, with differential distribution: clothianidin only in females, thiamethoxam predominant in webs with prey remnants, and acetamiprid/thiacloprid/imidacloprid present in all three matrices. Chlormequat was among the most abundant compounds detected.

Taxonomic history

Originally described as Theridion impressum by L. Koch in 1881; later transferred to Phylloneta.