Eumerus, Meigen, 1822

Adomako, Abigail Kusiwaa, Gasu, Edward Ntim, Mensah, Jehoshaphat Oppong & Borquaye, Lawrence Sheringham, 2020, What do Eumerus Meigen larvae feed on? New immature stages of three species (Diptera: Syrphidae) breeding in different plants, Organisms Diversity & Evolution (New York, N. Y.) 20 (2), pp. 267-284 : 278

Eumerus hoverflies feed on a wide range of plant tissues, not only bulbs

The variety of suitable plant tissues immature Eumerus are able to feed on also explains their polyphagy. Eumerus early stages interact with many different plant tissues, being bulbs, fruits, stems, and swollen roots the most common interactions ( Fig. 9 ). Species like E. amoenus and E. strigatus are the most diverse ones, feeding on five different types of plant tissues. While E. amoenus interactions with plant tissues are almost equally balanced, E. strigatus was more commonly related to bulbs rather than to other types of tissues. Almost an alike situation affects E. figurans and E. obliquus , the first one having almost equal interactions with four types of plant tissues and the second one attacking more fruits and aerial stems than tubers or processed materials. Some Eumerus species were only reported from single plant tissues, being the stem the most repeated one in these cases (nine species), followed by bulbs (five species) and swollen roots (four species). At the other end, we find that none Eumerus species has been report- ed to exclusively feed on tubers, rhizomes, fruits, or processed plant materials. Some special cases are those of E. figurans and E. superbus . E. figurans was the only species ever report- ed from corms, a special type of underground storage organ, midway between bulbs and tubers; E. superbus was the only species ever reported from gymnosperm cones.

Even though our findings appreciate that many types of bulbous plants are hosts for Eumerus , underground organs are, in general, suitable habitats for their larvae. However, bulbs and stems are equally reported as host tissues for 11 species of Eumerus larvae. In fact, if we consider all stems botanically, the addition of underground stems with structural function (rhizomes) and storage function (tubers and corms) to aerial stems (in green) conform the largest group of stem feeding Eumerus species. We do not include bulbs in this group because their stems are reduced to a minimum disc and it is covered by many layers of leaves with storage functions. These leaves are what Eumerus larvae mainly attack and dig through when entering a bulb, and, therefore, stems are not the majority of the biomass in these cases.

Figures

Fig. 9 Feeding network between larvae of Eumerus species (left, in gray) and plant tissues they feed on (right, colored) based on the interactions historically reported in bibliography for different genera of plants. Links between sides indicate relationships. Scales on each segment show the number of interactions established with the counter side. Plant tissue color palette as follows: tuber (yellow), swollen root (orange), rhizome (brown), processed material (black), fruits (red), stem (light green), corm (purple), cone (pink), and bulb (blue). Picture made using “circlize” package for R software