chapter 15 Lepidoptera (Moths and butterflies)

Ole Karsholt, Niels P. Kristensen†, Thomas J. Simonsen and Matti Ahola1

In terms of currently described species (150.000+, is referred to in the following succinct account focusing Nieukerken et al. 2011) the order Lepidoptera is the third- on structures useful in identification. Not all specialized largest of the 4 ‘megadiverse’ insect orders2; so it is in terms used in keys and descriptions are explained Greenland, but its representation here is very modest. here; reference should be made to the morphology Adult Lepidoptera are immediately recognizable by the glossary. dense scale-covering of the wings, which confers on the On the head the compound eyes account for a latter a more or less elaborate colour pattern. The body major part of the surface area; the median ocellus is and legs also have a dense scale and/or hair vestiture, consistently absent, while lateral ocelli are of variable which has no counterpart in other Greenland insects. occurrence. Antennae are always well developed, and in Almost all adult Lepidoptera (all in Greenland) feed several moths the flagellum (sometimes in males only) on fluid substances, particularly nectar and honey- is pectinate/bipectinate, while butterflies are unusual by dew (the sugar-rich fluid excrements of sternorrhynchan having the flagellum apex more or less abruptly thick- Hemiptera), or they do not feed at all, and hence are short- ened. A ‘chaetosema’ is a useful diagnostic feature of living. The vast majority of lepidopteran larvae (‘caterpil- some higher taxa; it is a ± convex cranial area located lars’) are herbivores, but some are fungivores or feed on behind the antennae and bearing a distinctive seta ves- other organic material; in Greenland they are all terres- titure (Fig. 1B). The mandibles are non-functional, small trial. They can almost always be immediately distin- to minute protuberances, and the adult insects can feed guished from other insect larvae by their complement of on fluid substances exclusively. The feeding apparatus is crochet-bearing abdominal prolegs (see below). The feed- a remarkable type of proboscis (‘tongue’) formed by the ing style and ± pronounced host specificity of several two maxillary galeae which are linked together by cutic- Lepidoptera larvae facilitates species identification. ular processes; the inner surface of each galea is con- cave, hence the coapted galae enclose a canal between them. In repose the proboscis is spirally coiled (Fig. 1C); Morphology: adults it can be extended by blood pressure, while recoil is due to wall elasticity combined with contractions of intrin- While members of the most basal extant families in this sic muscle fibres. Some moths do not feed at all in the order are quite generalized endopterygote insects, the adult stage, and in these the proboscis may be highly bulk of the lepidopterans, including all Greenland repre- reduced. Among ditrysian Lepidoptera only some sentatives, belong to the subordinate taxon Ditrysia, which Tineoidea (in Greenland Monopis) have retained promi- is characterized by a suite of remarkable specializations nent maxillary palps; in all other they are small, some- evolved on top of those pertaining to the lepidopteran times barely identifiable. In contrast, the labial palps in ground pattern. Only this advanced morphology type Greenland Lepidoptera are almost always well devel- oped and often very prominent (Fig. 1A, note that the 1 OK prepared the first draft of the taxonomic treatment. TJS & MA term ‘palp’ in most Lepidoptera literature will apply to contributed drafts of the keys to (and some descriptive notes on) the these only); their structure and vestiture often provide larvae; the habitus figures of the latter are mostly from Scandinavian useful taxonomic characters. specimens supplied by K. Silvonen. NPK drafted most of the introduc- The prothorax is considerably smaller than the pterotho- tory sections and some keys to adults, amalgamated the other authors’ racic segments, and of the latter the mesothorax is the dom- contributions and revised them more or less extensively in the pro- inant one. This is related to the fact that two wing pairs in cess. The definitive version is due to the collaborative efforts of NPK most ditrysian Lepidoptera are effectively coupled and and OK; unpublished observations (largely made on live specimens during the ‘Kissavik’ expedition by the latter are demarcated by (OK). the mesothoracic muscles moving the forewings are the 2 It may, however, be safely assumed that on a global scale it will even- principal flight motor. The wing coupling device is usually tually prove to be the least species-rich of the four, as is known to be sexually dimorphic: In males a hook-like cuticular lobe, the the case in the best inventoried part of the world, viz., NW Europe. ‘retinaculum’, arising from the lower surface of the anterior 15. Lepidoptera (Moths and butterflies) – Karsholt et al. 303 part of the forewing base grips a stout bristle, ‘frenulum’ retracted into the preceding segment. It comprises a ventral (actually a composite structure formed through fusion of sclerotization, the vinculum, which posteriorly articulates several adjacent bristles), arising from an elevated socket with sizable paired clasping ‘valves’ (likely derivatives of the on the basal front margin of the hindwing. In females the segmental appendages), while its upper ends articulate frenulum typically comprises a number of discrete bristles, with/are synscleritous with the dorsal sclerotization of the while the retinaculum analogue is a group of more or less segment, the tegumen. The latter in turn articulates with, or stiff, forwards-directed scales or hairs on the mid/posterior is synscleritous with, a variably shaped process, the uncus, part of the forewing underside base. Examination of frenu- which is formed by tergum X. Below the uncus lies the lum structure (males single, female multiple) hence often (partly membranous) anal cone, which morphologically is permits a most convenient rapid sexing of ditrysian moths the most posterior part of the body. The intromittent organ whose genital segments may be strongly retracted in dead (phallus) is a sclerotized tube enclosing an eversible ‘vesica’, specimens, but atypical cases do occur; for instance, the which often bears characteristic spines (‘cornuti’); it is situ- phycitine pyralids have but a single female frenulum bristle. ated between the valves and can be ± extensively protruded The butterflies lack a special wing-coupling device but still during copulation (Figs 10A-B). move the (basally considerably overlapping) two wing pairs The tip of the female abdomen (Figs 10C–D, 11C & F) as an entity. The scales along the apical and posterior wing bears 2 lateral, ± hairy and sclerotized lateral lobes, the ‘anal margins (and in many smaller moths also on the greater part of the front margin) are often long and slender, hair- like; they are then referred to as ‘fringes’ or ‘cilia’. In resting moths the forewings usually hide the hindwings, and only on the former is an elaborate pattern developed; in contrast, butterflies in repose fold their wings, uppersides- against-uppersides, over the body, and their wing under- sides (of the hindwings in particular) are also elaborately AB patterned. Wing patterns are very diverse within the order. Very often there are more or less prominent transverse fas- ciae, and a ‘median’ spot located at the outer margin of the discal cell is similarly recurrent. In most noctuids and also in some pyraloids this spot is more or less pronouncedly kidney-shaped, hence referred to as the ‘reniform stigma’; in the same taxa two more proximal markings are termed, respectively, the ‘orbicular stigma’ (inside the cell) and the ‘claviform stigma’ (below the cell). The legs are overall CD E unspecialized except that the fore tibia usually carries, near mid-length, a small appendage, the ‘epiphysis’, used for Figure 1 Taxonomically informative structures of adult grooming the antenna. Leg vestiture and spinosity may fur- Lepidoptera. A, gelechioid head (Bryotropha), nish useful identification characters. lateral view, showing large, upcurved labial palps In an extended abdomen of both sexes 9 segments are and scale-covered basal part of proboscis. immediately recognizable in dorsal view, whereas on the B, tortricid head (Acleris), lateral view, showing ventral side of segment I (hidden above the backwards ocellus adjacent to upper margin of compound eye, extending hind coxae) is much shortened and devoid of and chaetosema (with delicate hair-scales, here any sclerotization; in repose the terminal abdominal seg- bluish) immediately behind. C, tortricid head ments are often partly/largely withdrawn into segment VIII. (Acleris), anteroventral view (one labial palp While examination of the genital segment is of para- removed beyond basal segment), showing coiled mount importance for identification of Lepidoptera spe- proboscis and ‘tortricid-type’ head scaling (scales cies in many parts of the world, the overall depauperate on lower median part of head-capsule pointing Greenland fauna comprises very few species groups inwards-upwards). D, gelechioid hind tibia whose members, when well preserved, cannot easily be (Agonopterix), showing dorsal vestiture of distinguished on external features alone. long, raised hairs. E, pyraloid hind tibia The most conspicuous parts of the male genital appara- (Gesneria), showing dorsal smooth vestiture tus pertain to segment IX; this apparatus is generally ± of appressed scales.