Nectar Meals of a Mosquito-Specialist Spider

Abstract

Evarcha culicivora, an East African jumping spider, is known for feeding indirectly on vertebrate blood by actively choosing blood-carrying mosquitoes as prey. Using cold-anthrone tests to detect fructose, we demonstrate that E. culicivora also feeds on nectar. Field-collected individuals, found on the plant Lantana camara, tested positive for plant sugar (fructose). In the laboratory, E. culicivora tested positive for fructose after being kept with L. camara or one of another ten plant species (Aloe vera, Clerodendron magnifica, Hamelia patens, Lantana montevideo, Leonotis nepetaefolia, Parthenium hysterophorus, Ricinus communis, Senna didymobotrya, Striga asiatica, and Verbena trivernia). Our findings demonstrate that E. culicivora acquires fructose from its natural diet and can ingest fructose directly from plant nectaries. However, experiments in the laboratory also show that E. culicivora can obtain fructose indirectly by feeding on prey that have fed on fructose, implying a need to consider this possibility when field-collected spiders test positive for fructose. In laboratory tests, 53.5% of 1,215 small juveniles, but only 3.4% of 622 adult E. culicivora, left with plants for 24 hours, were positive for fructose. These findings, along with the field data, suggest that fructose is especially important for early-instar juveniles of E. culicivora.

Wandering and web spiders feeding on the nectar from extrafloral nectaries in neotropical savanna

“…All the seven families tested in this study presented fructose‐positive individuals. Six of these families had already been described in other studies as being nectar consumers (Taylor & Pfannenstiel, ; Chen et al ., ; Kuja et al ., ). Theridiidae species had not been found feeding on nectar yet.…”

“…In this study, the fructose detected in spiders’ bodies may originate from floral or EFNs. There is also the possibility that nectarivorous insects have transferred some fructose to spiders – acquired by them short before being eaten by spiders (see Kuja et al ., ). However, we often observed the presence of spiders quite close to the EFNs and sometimes they had their mouthparts on them, thus indicating nectar feeding.…”

Ontogenetic shift in plant-related cognitive specialization by a mosquito-eating predator

“…In laboratory olfactometer experiments (Cross and Jackson, 2009b), adult females, adult males and juveniles from all size classes were attracted to the odour of two plant species, L. camara and R. communis . The juveniles of E. culicivora are especially inclined to feed on nectar when they visit plants (Kuja et al, 2012) and there is a specialized relationship between nectar meals and predation on mosquitoes: after nectar meals, the juveniles of E. culicivora become more effective at subduing the mosquitoes they attack (Carvell and Jackson, 2015). However, we propose that mating instead of feeding is the context in which E. culicivora adults make specialized use of plants.…”

“…Adults, but not juveniles, are also attracted to cineole, albeit less strongly than to caryophyllene and humulene. Another juvenile-adult difference is that, after a fast, the juveniles but not the adults of E. culicivora become more strongly attracted to the odour of caryophyllene and humulene (Nelson and Jackson, 2013; Kuja et al, 2012), with the benefits of nectar meals for juveniles including rapid improvement in their prey-capture efficiency (Carvell et al, 2015). Although the role of plants in the biology of adults is less well understood, natural-history observations suggest that L. camara might be important as a mating site (Cross et al, 2008).…”

Mosquito-terminator spiders and the meaning of predatory specialization

“…Our solution was to present a test odor in conjunction with a masking odor. The masking odor came from Lantana camara (L.), a plant species that E. culicivora visits for nectar meals (Kuja et al 2012), and it is known that E. culicivora detects the odor of this plant species (Cross & Jackson 2009aNelson & Jackson 2013). ''Conspicuous'' meant that no masking odor from L. camara was present.…”