Several weeks ago, I observed some unidentified pupae (Fig. 1) on a Mecardonia procumbens (Yellow-flowered Waterhyssop) plant in a pot located on my balcony. These pupae possessed two horns at one end, reminiscent of a similar observation I made in 2015 on a Hibiscus plant that was also infested with aphids. At that time, I hypothesized that these pupae might belong to the Hover Flies (family Syrphidae). However, the recent discovery suggests that they may be from another group of flies, specifically Aphid Flies (family Chamaemyiidae).

Fig. 1: Pupa of Aphid Fly	Fig. 2: Aphid Fly (Chamaemyia sp.)

I was unaware of the existence of a group known as Aphid Flies until I encountered related information on the UC IPM website while investigating the unknown pupae. The website contains images of an aphid fly (Chamaemyia sp.) and its pupa that resembled those observed on my aphid-infested plant. Upon researching further images of Chamaemyia sp. from the iNaturalist website and comparing them to my archived fly images, I discovered a match with an unknown fly (Fig. 2) that I photographed in my balcony area in 2020.

With the new insights on Aphid Flies, a family under the order Diptera (Flies), I was prompted to conduct a comprehensive review of all the fly images in my Diptera page. This involved cross-checking them with the images from the iNaturalist website, specifically focusing on records from Singapore. Consequently, I made substantial updates to the potential identifications of many of the fly images in my Diptera page. While errors are inevitable due to my limited knowledge, it is hoped that any misidentified species will be corrected over time.

Following the updates to my Diptera page, I embarked on a walk in a nearby park to examine the fly population on 16 March. The outing proved to be productive despite the cloudy Sunday morning. A total of eight fly species across seven families were identified (Fig. 3): Long-legged Fly (Chrysosoma sp.), Blow Fly (Hemipyrellia ligurriens), Signal Fly (Rivellia sp.), Flesh Fly (Sarcophaga sp.), Stilt-legged Fly (Mimegralla albimana), Lauxaniid Fly (Minettia sp. and Prosopophorella sp.), and House Fly (Lispe sp.). The most abundant species observed during this excursion were the Blow Fly and Flesh Fly, although they were typically seen as solitary individuals rather than in groups. Notably, both Prosopophorella sp. and Lispe sp. are new additions to my Diptera page.

(a) Chrysosoma sp.	(b) Hemipyrellia ligurriens	(c) Rivellia sp.	(d) Sarcophaga sp.
(e) Mimegralla albimana	(f) Minettia sp.	(g) Prosopophorella sp.	(h) Lispe sp.
Fig. 3: Eight species of flies (a - g) from 7 families observed during the park walk

Fig. 4: Aphid Fly (Leucopis sp.)

Meanwhile, I have continued to monitor the aphid-infested plant in my pot, aiming to spot the fly and the larva. My efforts were rewarded when I spotted a tiny fly (Fig. 4) on the leaf of Cardamine occulta (Nursery Bittercress), which was growing in the same pot as Mecardonia procumbens. After comparing the images obtained with those on the aphid fly images in iNaturalist website, it appears to be an aphid fly (Leucopis sp.). However, there is no conclusion regarding its relationship with the pupae observed on Mecardonia procumbens.

Besides the flies, various other minibeasts from different groups were seen during the park walk. I plan to share the rest of these encounters in a subsequent post.