DIPTERA > BRACHYCERA | Higher Diptera

MUSCOMORPHA > ASCHIZA >  Syrphoidea > Syrphidae > Eristalinae > Eristalini

The Eristalini tribe comprises 8 genera and 28 species all with the distinctive loop in wing vein R4+5. The previous page covered the largest genus Eristalis, and here I'm currently able to feature three more. 

Anasimyia

Although this genus includes five recognised species, only two are normally considered, Anasimyia lineata and Anasimyia contracta. Two of the others are nationally scarce and have never been recorded in my area, whereas the remaining species Anasimyia transfuga could. It has very similar markings to Anasimyia contracta, but with T2 being narrowed. Anasimyia contracta is the most frequently observed member of the genus although, whilst widespread and relatively common, it is a local species that will only be found in certain wetland habitats.  

Myathropa

This is another genus only represented by a single species, Myathropa florea. It has a distinctively marked body with the thorax having a dark area towards the back resembling the 'batman' symbol. Well-marked individuals are quite striking, but the markings are variable such that some may be confused with other Eristalini species.    

Helophilus

There are five Helophilus species, two of which are vagrants that have only been recorded in Scotland, so only three need to be considered, Helophilus hybridus, Helophilus pendulus and Helophilus trivittatus. Although shared with the closely-related genera Anasimyia, Lejops and Parhelophilus, Helophilius species can be identified by the characteristic loop in wing vein R4+5 coupled with the distinctive pale longitudinal stripes on the thorax, which has given rise to the generalised name of 'tiger hoverfly'. Their black antennae separate them from Anasimyia and, more importantly, from the not dissimilar Parhelophilus species, both of which have orange antennae. And, although there's not much chance of confusion with the scarce Lejops species that has not been recorded locally, Helophilus has a single dark ring on the hind tibia, whilst Lejops has two.

Distinguishing the different Helophilus species relies on the identification of specific features (as given in the book), which can only be done once the sex is known. Normally that's quite easy by looking at the eyes, but that's not possible with Helophilus as they are separated on the top of the head in both sexes. You have to look at the abdomen and determine whether a genital capsule is evident, obviously confirming that the individual in question is a male, but that can only be done if the photo has been taken from the right angle. In general, once the sex is established it's easier to identify males to species than females. Fortunately, there's usually an expert on the FB group that can confirm the species if in doubt.

Sept.24