Lucas Rubio collaborates in the arthropod section
My relation with insects is not very long. I am studying biology at the University of Buenos Aires and I have been taking macro photos of arthropods for some years now. Enough to get familiar with various groups of insects and the corresponding bibliography to identify them. To contact the author: [email protected]
Athropods have an exoskeleton and jointed appendages. In general people categorize all these animals as insects and it is a mistake. Insects are only one of the classes within arthropods. Arthropods also comprise the arachnids, the crustaceans and the miriapods. A simple way not to confuse them is to count the number of legs. Insects have three pairs of legs; arachnids, 4 pairs (and no antennae); crustaceans, 5 pairs and the miriapods, many more pairs of legs.
The primary objective of this site is to insert insects within the Costanera Sur World. To understand them as interactive components of the system, preys, predatos, polinators, etc. To reach the species level of an insect is on many occasions impossible either because the photo does not show the diagnostic character or because genitalia is required to get to this definition level.
Those who want to send photos of insects may subscribe to Artrópodos Argentinos. A group of enthusiastic entomologists help to unravel this intricate world. One of them is Gastón Zubarán who collaborated in this site and keeps doing so indirectly through Artrópodos Argentinos.
Insects have a chitinous exoskeleton, two antennae, three pairs of legs and two pairs of wings. Their body is organized in three segments or tagmata: a head, a thorax and an abdomen. It is important to bear in mind the number of legs rule not to call them insects erroneously just because they are segmented.
They are not glamorous nor do they inspire tenderness. Most people hate them. They feel repulsion and try to exterminate them by any means. They are the enemy. This is so because we only bear in mind those which cause harm or negatively affect our daily life and we do not know all the benefits they may carry directly or indirectly. The colourful butterflies and some beetles may be the exception. Only the harmful, beneficial or nice may bear a name. That is why insects have been grouped under a generic name. In this way one can associate the belonging of an insect inside a group, even if we do not know the species for certain.
They outnumber us widely. More than half of all described species and three quarters of all the animals are insects. It is said that there are 200 million insects per inhabitant and we barely perceive a few. Their small size or perfect camouflage contribute to their anonimacy. Neither does it help the behaviour of a birdwatcher who move away to see the object and overlook these small creatures when observers lose contact with plants. Nevertheless, all insects have a characteristic as inexplicable as fascinating: the curious transformation which undergo many of them turning into a completely different organism. A wingless caterpillar which devours leaves becomes a flying butterfly which laps up flowers. The entomology, the science which studies them, is a discipline in constant revision and investigation. And there is a lot to explore.
Butterflies and moths were the first insects listed on this site and they remain in a separate section. Butterflies' names in Spanish have been taken from the book "Mariposas de la Ciudad de Buenos Aires y alrededores" by Ezequiel Núñez Bustos, who collaborates in the lepidopteran section. To visit the cast of Lepidoptera click on the photo.
|Lepidoptera (Butterflies and moths)
Multicoloured Asian Lady beetle
Metallic blue lady beetle
Shining leaf chafer
Soft-winged flower beetle
Soft-winged flower beetle
South American fruit tree weevil
Fuller's Rose weevil
Sesbania clown weevil
False click beetles
Golden tortoise beetle
Large diving beetle
Hymenoptera (Wasps, bees and ants)
Potter and paper wasps
Black paper wasp
Small carpenter bee
European honey bee
Chimney bee cuckoo
Leaf cutter bee
Leaf cutter ant
Hemiptera (True bugs; cicades and spittlebugs; aphids)
Black bean aphid
Scentless plant bug
Tomato stink bug
Black and red bug
Jagged ambush bug
Diptera (flies, mosquitoes)
Band-eyed drone fly
Toxomerus cf. duplicatus
Efferia (s.l.) sp.
Grizzled woodlouse fly
Odonata (Dragonflies and damselflies)
Orthoptera (locusts and crickets)
The Order Orthoptera is composed of two groups: Ensifera and Caelifera. In general terms they are known as locusts and crickets respectively.
They are hemimetabolous insects. They undergo different stages, but they look like their parents since they are born.
If crickets and locusts are famous for something is for their ability to jump. Of the three pairs of legs only the posterior one, which is very strong, is designed for jumping. It has springs which together with the muscle accumulate the energy which is released when the insect is eyected. They use jumping as a way of escape, fight or a simple way of moving.
Another characteristic typcal of this order are the sounds produced by rubbing body parts. In crickets the stridulating mechanism is on the forewings. In locusts it may be on the wings or on the legs. Song is used in pair formation or as an indication of allarm or aggression.
A good song needs a good ear and the location of the ear also differs in locusts and crickets. The crickets' "ear" is on the frontal tibia and the locusts' on the first abdominal segment.
The more basic difference between these two groups is the length of the antennae. Crickets have more than 30 segments and locusts less than that. Roughly speaking, long antennae is a cricket, short antennae is a locust.
Ensifera's ovipositor is scimitar-like or cylindrical. It is inserted in vegetal tissues or the ground (respectively) to lay eggs. In general eggs are laid separately. Caelifera's ovipositor is short and dented. They dig a hole and introduce the ovipositor which elongates doubling almost its size thanks to specialized muscles.
Lesser meadow katydid
Minute green mantidfly
Arachnids are as difficult as insects. You can find help in the indentification or important information in Reivindicando a las arañas (Vindicating the spiders).
The arachnids (spiders, scorpions and mites) have a body organized in two segments or tagmata (a cephalothorax and an abdomen), four pairs of legs, a pair of chelicerae and a pair of pedipalps. Generally they are erroneously considered insects If people dislike insects, spiders take the worst part. There is a phobia which is reinforced by a ruthless image of spiders. To come across a web causes excessive panic. Nevertheless, in most cases they are timid and avoid our presence. Not all of them weave a web, but all of them produce a silk thread which may have different functions. They are of immense benefit to man since they catch lots of insects.
Golden Silk Orbweaver
Red spider weaver
Social cobweb spider
Giant crab spider
Giant crab spider
Giant crab spider
Running crab spider
Unlike insects and spiders, the crustaceans have a good reputation. As they are primarily aquatic we have no contact with them. On the ohter hand, the are well appreciated as food.
The crustaceans have a body protected by a calcareous exoskeleton and is divided into two or three segments depending on whether the head is fused to the thorax, in which case the cephalothorax is formed, and the abdomen. They have two pairs of antennae and one pair of mandibles. As the number of legs goes they may be decapods (five pairs of legs) or may have several legs
The myriapods include all the animals which are commonly called centipedes and millipedes and which are recognized by their highly segmented bodies with too many legs. The centipedes comprise scolopendrids.
To tell apart a centipede from a millipede is easy. Pay attention to the number of legs at each segment. If there are four (two on each side of the segment) it is a millipede. Otherwise, one leg at each segment makes it a centipede. Another clue is their behaviour before a threat. The centipede escapes, whereas the millipede rolls up and stays quiet or protects itself by secreting some toxic or irritating chemical. A third clue is the disposition of the legs which spread away in centipedes and fall to the ground in millipedes.
The myriapods live only on land. Most of millipedes prefer humid places since their exoskeleton lacks a waxy layer which retains water. The centipedes may be found in all hábitats, including deserts where the largest species are encountered. The centipedes are predators and hunt primarily at night They feed on other invertebrates. The millipedes mainly eat rotting organic matter.
They are not considered dangerous to man, but you should always take special care. The bite of the largest millipede species may cause discomfort such as, vomitting, fever, etc. The millipedes do not bite but they secrete poisons though in rather small quantities for us to casuse an alarm. Anyway, it is advisable to wash thoroughly.