Skip to main content

#49: Spider Mites


Litinsects #49:

Month of Mites, Part 5

Let me introduce you to some pesky little dudes called spider mites. There are about 1200 species of spider mites and they are huge agricultural/commercial pests. The TWO-SPOTTED SPIDER MITE shown in these photos (named for, you guessed it, its two dark spots) is one of the most well-known and economically important pests worldwide because it feeds on hundreds of plant species. I worked with these mites as part of my master’s thesis and was able to witness firsthand how they can decimate plants if left uncontrolled!
 
  • So why are they called spider mites? Because they spin silk WEBBING that can cover entire plants. The webbing serves as protection for the colony from weather, desiccation, and pesticides but also protects from predators, who can’t maneuver through it very well
     

  • Spider mite females are larger, at around 0.5 mm and males are around 0.3 mm. The eggs are round and 0.15 mm in size. Just before hatching, the mites’ RED EYES are visible inside the eggs! 
     
  • Spider mites feed by penetrating plant epidermal cells and sucking out the contents, leaving characteristic pale patches on the leaves. A few empty cells here and there might not be a big deal but as you can imagine, the appetite of an entire colony will soon result in huge areas of empty plant cells, which eventually kills the plant due to its inability to photosynthesize
  • An interesting phenomenon seen in spider mites is ARRHENOTOKY, which I explained using the term HAPLODIPLOIDY in my post about hymenopterans (Day 33). This means that males are produced from unfertilized eggs and females are produced from fertilized eggs
  • Studies have found that these mites can probably RECOGNIZE who they are related to in order to avoid inbreeding! When given a choice between two males in an experiment, one related and one not related them, females were more likely to mate with the one they were not related to, pointing to some mechanism for recognition
  • And finally, as I first mentioned in my aphid post (Day 30), this mite is the only animal species besides aphids known to produce CAROTENOIDS themselves. All other animals get these red/orange pigments from plants or algae they ingest. Two spotted spider mites can do it thanks to a gene transfer millions of years ago from fungi!
Labels:

Comments

Post a Comment

Popular posts from this blog

#4: Simple Eyes

Litinsects #4: Simple Eyes Yesterday I talked about compound eyes, the multi-faceted structures that most insects use to see the world 👀 But insects actually have another visual system as well, composed of simple eyes or OCELLI. Unlike compound eyes, ocelli are composed of only one structure which makes them comparatively “simple” although they are still very important. These are light-detecting organs consisting of a single lens with sensory cells. They can detect movement but don’t form complex images. “Ocellus” comes from the Latin word oculus, meaning eye. So these structures are literally “little eyes” Ocelli are located on the insect’s head, usually between or adjacent to the compound eyes. They are usually dome-shaped, somewhat shiny structures In most flying insects (such as flies, dragonflies, bees, etc.) there tend to be three ocelli in a triangle arrangement (see photo). Some terrestrial insects (like cockroaches) have only two ocelli ...
Post a Comment
Read more

#34: Insect Wings

Dragonfly wings Dipteran (fly) wing Monarch butterfly wing Lacewing wings Litinsects #34: Insect Wings Let’s talk wings. The ability to fly has existed in only 4 groups of animals: birds , bats , pterosaurs , and of course insects . The first three groups, all vertebrates, each evolved flight independently (in other words, they have no winged ancestor in common) and the wings replace a pair of limbs. Insect wings on the other hand, which first showed up around 400 million years ago, are not derived from legs but are completely separate structures. The big debate about the evolution of insect wings is whether they developed from pre-existing structures (like gills or extensions of the thorax) or were entirely new structures. There is very little fossil evidence documenting this evolutionary transition so no one has yet definitively answered this question... Insect wings attach to the second and third thoracic segments. At rest they may be held vertically over the back, horizontally ou...
Post a Comment
Read more

#51: Mayflies

Litinsects #51: Mayflies Mayflies are aquatic freshwater insects and belong to one of the most primitive winged insect lineages! First off, what’s in a name? Mayflies’ common name comes from the fact that some species start “hatching” from the water in May. But their scientific name is much more interesting and accurate; this order is named EPHEMEROPTERA from the Greek “ephemera” for “lasting one day / temporary” and “pteron” for “wing”. A more fitting name would be dayfly, considering their adult lifespan... Most live less than 24 hours after emerging, the shortest adult lifespan of any insect! -Mayflies have triangular-shaped wings that are held upright over their bodies when at rest (sort of like a butterfly) and have three long tail-like filaments. These characteristics, both of which make them easily recognizable, are probably traits that were present in the most primitive flying insects -They are HEMIMETABOLOUS insects, meaning they go through incomplete metamorphosis, with multi...
Post a Comment
Read more