#1631-1634 - Beetles
#1631 - Diamesus osculans
Photo by Pete Hayhoa in the Tiwi Islands, north of Darwin.
Diamesus osculans is a rather large Silphid beetle, and the Silphids are already known as Large Carrion Beetles. There are two species in Tropical Asia and Australia, but D. osculans is increasingly rare on the Australian mainland, probably because of habitat destruction and the reduction in the number of large dead mammals lying around the landscape.
The larvae are large and flat and resemble cockroachs, and are voracious predators of maggots.
The family is divided into two subfamilies, the Nicrophorinae and the Silphinae. The later, broadly known as Burying Beetles, include the endangered North American Nicrophorus americanus. Nicrophorine beetles try to arrive at a body before the maggots are established, and in many species will bury a small corpse underground in order to monopolise the carrion. They’re also highly unusual among insects in that both parents will care for and feed the young - in same cases, on a larger corpse, multiple females will share childrearing duties, if the number of fly maggots threatens to get out of control. Silphine beetles, on the other hand, arrive later, and may eat so many of the maggots that it can be difficult for a forensic examiner to determine the time of death.
In both groups beetles may contest bitterly over potential feeding sites, driving off rival males or pairs. Winged species generally target vertebrate corpses while flightless and sometimes-flightless species target soil invertebrates. Some Silphids will attack human crops as a secondary food source - Aclypea opaca in Europe feed on beets, and Necrophila americana on pumpkin, spinach, and sugar beet.
Silphids protect themselves with warning colours and foul-smelling secretions. In the species Necrodes surinamensis the beetle will rotate the end of its abdomen to spray the chemicals in all directions.
#1632 - Fam. Lampyridae - Firefly
Another one from the Tiwi Islands, north of Darwin. Photo by Craig Winston.
Fireflies aren’t common in Australia (and becoming more rare with habitat destruction and light pollution, which is a problem worldwide) but we do have a decent range of genera. I’m not sure which one this is, since the shape and orange-and-black colouration is pretty standard, although the way the light-emitting organs are limited to one and a half abdominal segments is a little unusual, compared to the images up at the Atlas of Living Australia.
There are over 2000 species of Lampyrid beetle in the world, but not all of them produce bioluminescence, and whether it’s the larvae, the adults, or the male or the female that produces the light varies widely from species to species. In many species, the females are larviform, lacking wings. In some parts of the world the larvae and larviform females are called ‘glowworms’. The light is usually green, yellow, or pale red.
Firefly larvae, which are usually nocturnal, glow to warn predators of their noxious taste. Adults use the light to identify mates of their own species, although Photuris females hijack this system by flashing in responce to the mating sugnals of other species, then eating the unfortunate hopeful that shows up. Some species of firefly group together by their thousands, in a single tree, and flash in synchrony.
Firefly larvae are general specialised predators of other larvae, snails, and slugs. Adults have a more varied diet, or may not feed at all. The European glow-worm beetle Lampyris noctiluca, for example, lacks a mouth.
#1633 - Fam. Lampyridae - Firefly
Photo by Sara Stephens-Huddleston, at Northerm Rivers, NSW.
Either a larval firefly, or the larviform adult female - I’m not sure. I depends entirely on what species it is.
#1634 - Subfam. Cicindelinae - Tiger Beetle Larva
Photo by Peter Hayhoa in the Tiwi Islands, north of Darwin.
The records for tiger beetles up that way include Cicindela (Archidela) darwini (which makes sense) and Australicapitona australasiae (also a good name), but since I can’t find pics of the larvae of either, I’m not going to go past subfamily. Not least since they were demoted to a subfamily of the Carabidae and the published literature on their taxonomy is an appalling mess.
Tiger Beetles are highly predatory Ground Beetles, with large eyes and, usually, long legs. The move so quickly that they can’t process what they’re seeing without stopping to think, leading to a distinctive dash-and-pause run as they pursue prey and recalculate which way to run. Wisely, they hold their antennae out in front of them as they sprint, to avoid running into obstacles at top speed.
Tiger beetles larvae, on the other hand, live in cylindrical burrows up to a meter deep. They are large-headed, fearsomely jawed, and hump-backed, and use their humpbacks to grip the sides of their tunnels as the lunge out at any passing prey. While they wait, their heads fit snuggly into the burrow, and their eyes are positioned to peer in all directions.
Some tropical species are arboreal, but most live on the ground along shorelines, on sand dunes, around dry lakebeds and on clay banks or woodland paths, being particularly fond of sandy surfaces as in the photo here. That said, being unearthed from their burrow is a problem, so at least one beach-dwelling species, Cicindela dorsalis media, will flip intself into a circle and roll off across the beach at high speed, driven by the wind.