Blood-finding strategy of a capillary-feeding sandfly, Lutzomyia longipalpis.

Salivary gland homogenates of adult female Lutzomyia longipalpis inhibited platelet aggregation induced by ADP and collagen. Apyrase (ATP diphosphohydrolase) activity was prominent, requiring Ca2+ but not Mg2+ and a pH optimum of 8.0. Human as well as rabbit hosts developed a well delimited erythema, evident 2-3 min after initial probing and lasting for as long as 2 days. Erythema, not accompanied by itching or swelling, developed in previously exposed hosts as well as in those not previously exposed to this insect. When injected intradermally into the shaved back of a rabbit, salivary gland homogenates induced marked erythema, even with 1/250 of a homogenized salivary gland. This erythema-inducing factor was insoluble in 90% ethanol and was destroyed by incubation with trypsin. These apyrase and erythema-inducing factors, together with short mouthpart stylets, appear to adapt Lutzomyia sandflies to feed on blood released from superficial skin capillaries.