AEGERIIDAE. Introduction by Dr. A. Seitz. 
515 
22 . Family: Aegeriidae (Sesiidae). 
The Aegeriidae are a group of lepidoptera the exterior of which is most distinctly accomodated to a 
certain principle. They are lepidoptera transformed according to the general physical law for insects without 
an interior protection by copying well protected insects and have thereby lost all their lepidopteral resemblance. 
Even the chief characteristic feature of the lepidoptera, the scales of the wings, are often missing here nearly 
altogether. Traces of these scales, which are found on the emerging imago, but which are shaken off at the 
first trial of flight, give evidence of their original presence, and in fact there are yet single species which, owing 
to certain circumstances, have preserved their scaled exterior. Among the almost entirely diurnal Aegeriidae 
there also occur a few species with nocturnal habits, and although this nocturnal habit is undoubtedly a 
secondarily acquired exception (for instance in the genus Weismannia), we notice that the wasp-like exterior 
already begins to disappear in these noctural lepidoptera; the mostly distinct Hymenoptera-like mark of the 
wings is obscured in the same way as the Hymenoptera-like hyaline patches in the Weismannia- wings are 
covered again with a slight veil of scales, being the result of the transition of the insect to its nocturnal life 
in which mimicry is of no use. On looking at the plate 51 of Vol. II we at once see how very much the shadow¬ 
like coloured Weismannia agdistiformis contrasts with the other figures of the plate, all of which represent 
heliophile insects. 
Another reason why the original scaled exterior was preserved is that in the range of the Ethiopian 
Aegeriidae wasps or bees do not always represent the best protected insects and, thereby, the fittest models. 
The great predominance of yellow and black wasps with hyaline wings only occurs in the palaearctic and perhaps 
yet the nearctic regions. Already in North Africa the wasps with yellow abdominal rings and hyaline wings 
are considerably inferior to differently coloured Hymenoptera, and taking into account that the Aegeriidae 
number among the most adaptable insects we must not expect them to be transformed according to models 
of an inferior protection. The more the Ethiopian Aculeatae with dark or variegated wings predominate over 
the yellow-marked wasps (predominating with us), the more the Aegeriidae of these districts lack the yellow 
abdominal belts and the hyaline areas in the forewings. The Ethiopian Aegeriidae chiefly exhibit dark blue 
forewings in accordance with most of the African Pompilidae, many Sphegidae, also species of bees; Macro- 
tarsipodes liangi (77 a), Megalosphecia gigantipes (77 e), and many Melittia ( occidental ^, abyssinensis, 77 g, 
heckmannia 77 h), Cryptomima hampsoni 77 h, Paranthrene anthrax 77 h, Conopsia terminiphora show on the 
forewings the blue colour characterizing the wasps of their patriae. But not only the shape and colour of the 
wings have been copied from the Aculeatae, but also other organs are used for deception, particularly the 
hindlegs. The imitation of the “collecting-trousers” (exhibited by the bees bearing the pollen of flowers) by 
the Aegeriidae cannot be explained by any reason other than mimicry. In capturing Melittia bombyliformis 
(Vol. II, pi. 51 a) on blossoms in Shanghai I ascertained that these organs, i. e. the hind tibiae being provided 
with a thick brush, distinctly hinder the imago in drinking from blossoms with deep calyces. The insect forcing 
itself into the blossom in search of honey must stretch these hind tibiae posteriorly upwards and must keep 
the wings quiet so long, whereas in drinking from flowers without calyces it buzzes on like a Haemorrhagia. 
In such cases only the bee-like coloured abdomen of the Melittia and the trousers projecting from the calyx 
are to be seen; unless being closely examined (which is quite impossible with the instinctively acting enemies 
of lepidoptera) this deception will remain unnoticed both by animal and man. 
