How to identify a Christmas Beetle
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Is the specimen a Christmas Beetle?
The Christmas Beetles belong to the family Scarabaeidae, subfamily Rutelinae, genus Anoplognathus. To identify the genus Anoplognathus work through the following four steps:
Step 1. Is the specimen a beetle, Order Coleoptera?
To determine if the specimen is a beetle confirm the specimen:
- has 3 body parts
- a head,
- 3 pairs of legs
- 2 pairs of wings
- The forewings should be hardened into sheath like protective coverings
- These are called elytra that protect their delicate hindwings
- A tough exoskeleton
If it is a beetle, check whether it belongs to the family Scarabaeidae.
Step 2. Identification of the family Scarabaeidae
The family Scarabaeidae is large, consisting of around 2,300 genera and over 27,000 species worldwide (Cassis & Weir 1992).
The Australian Scarabaeidae possess the following characteristics (modified from Lawrence & Britton 1994):
- body not capable of rolling into a ball
- head not covered by pronotum (Figure 2[i])
- labrum or mandibles or both usually hidden below edge of head (Figure 2[i])
- less than 11 antennal segments (Figure 2[i])
- 3-8 segmented antennal club present and distinct (Figure 2[i])
- antennal club segments strongly asymmetric, often lamellate (Figure 2[i])
- foretibial spur single or absent (Figure 2[ii])
- fore coxae large, occupying most of underside of prothorax
- tarsi with 5 simple, unlobed, segments (Figure 3[iii])
- abdomen with 6 visible ventrites
Step 3. Identification of subfamily Rutelinae
The subfamily Rutelinae includes about 200 genera and 3800 species worldwide, of which 23 genera and approximately 109 species occur in Australia (Cassis & Weir 1992).
Adult Rutelinae can be distinguished by a combination of the following characteristics (Figure 3[i])
- unequal tarsal claws on hind leg (Figure 3[ii]).
- claws flattened and flexible (Figure 3[ii]).
- mesotarsus with 5 distinct tarsal segments (Figure 3[iii]).
- pygidium visible beyond apex of elytra.
- elytral epipleura with a membranous margin.
- at least one pair of abdominal spiracles exposed below elytral margin.
- head and pronotum without prominences (Figure 3[iv]). (Lawrence & Britton, 1994).
Step 4. Identification of the genus Anoplognathus (Christmas Beetles)
Christmas Beetles belong to the genus Anoplognathus Leach. Anoplognathus is endemic to Australia, except one species shared with New Guinea. There are 36 species, 21 of which occur in New South Wales (Cassis & Weir, 1992). Adult beetles feed on leaves, usually of eucalypts, and larvae feed on roots, usually of grasses. Several species are economically important pests in eucalypt plantations.
Anoplognathus can be separated from other genera of Rutelinae, in New South Wales, by the following characteristics (adapted from Carne, 1957,1958)
- foretibia with 1-2 lateral teeth (Figure 4[i]).
- metaventrite process projecting anteriorly between the mid coxae (Figure 4[ii]).
- tarsal claws simple, not toothed, in males (Figure 4[iii]).
- hindtibia not greatly enlarged (Figure 4[iii]).
- frontoclypeal suture distinct (Figure 4[i]).
- labrum not projecting beyond clypeus.
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