Question

Which type of mouth parts are mandibles entirely absent?

Answer 1

MANDIBULATE-LAPPING TYPE

Mandibulate-lapping mouthparts are linked to a liquid-based diet (e.g. nectar), even though in some cases they conserve the chewing function. They’re typical of hymenopterans. Sawflies or suborder Symphyta, considered the most ancient group of hymenopterans, conserve almost all original structures and functions of mandibulate mouthparts. Both wasps and bumblebees have undergone a reduction of both mandibles and maxillae and a massive development of labial glossae, forming a kind of tongue for drinking liquid food; however, they can still chew. Finally, bees have mandibles not for feeding, but for other purposes (such as fighting, grooming theirselves or working wax scales into honeycomb), and both maxillae and labial glossae lengthen giving room to a hairy tongue with an internal duct (the salivary duct), so their diet is exclusively liquid-based.


SUCKING-LAPPING TYPE

In this kind of mouthparts, mandibles undergo a massive reduction (and if present, they’re not for feeding purposes), even disappearing in some cases; so, insects with sucking-lapping mouthparts have a diet exclusively based on exposed liquids. There exist two main variations of this model: the ‘maxillar sucking’ or siphoning type typical of evolved lepidopterans and the ‘labial sucking’ or sponging type typical of flies and other dipterans.

In flies, mandibles are totally absent, maxillae are only represented by maxillary palps and posterior part of labium massively increase, forming two lobes which are sponge-like organs called the labella. The labella is a complex structure consisting of many grooves which sops up liquids much like a sponge does.


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