Happy Halloween!

The well-known hourglass marking of Latrodectus mactans, the black widow spider.

Happy Halloween!  Just for ringing the doorbell, I'm presenting you with these eight-legged treats!  Spooky you say?  I suppose it is a matter of perception, I think they are all lovely!  The black widow above has a potent neurotoxic venom, but her bites are rarely fatal for humans.  For insects that blunder into her web however, it is a different story.

The bolas spider below employs a different strategy.  She does not capture prey in a web, but rather forms her silk into a sticky blob on the end of a strand.  She swings this blob at moths that fly near enough to her.  To entice her quarry, she secretes a chemical that emulates pheromones that the moths use to attract mates.  She can even change the chemical signal to match the species of moths that are around.  I've never been able to decide which was cooler: the rodeo style hunt, or the complicated chemical mimicry.

A Mastophora species Bolas Spider hunts with a sticky blob on a silk strand.

 The bolas spider isn't the only spider with a unique method for capturing prey.  The net-casting spider spins a web that is not sticky but has a wooly texture which entangles insects.  It holds the web with its legs, and throws it down on unsuspecting critters that venture too close.

The wolf spider does not hunt with a web at all, rather they stalk their prey and pounce upon them.  Female wolf spiders carry their eggs with them, and when the young hatch, they continue to ride around on mom for a while.  Wolf spiders are frequent visitors in basements, where they eat many other arthropods that may be less welcome.  While a ball of baby spiders may sound like something out of a horror film, I find this parental care to be fascinating.  I'd even go out on an entomological limb and say that it's kinda cute!

Wolf spiders (Lycosidae) carry their young.

A Costa Rican net-casting spider in the family Deinopidae.

Way to go...

Stiretrus anchorago the Anchor Stink Bug, in copula, with a twist.

 The anchor stink bug is a predatory pentatomid species that is found in Delaware, but looks very little like a stink bug at first glance.  While taking care of a lab colony of these bugs this mating pair caught my attention.  I was soon amazed to see that the female was upside down, or I suppose she was right side up depending on your perspective.  I soon realized the cause of this bizarre mating arrangement:

um, was it good for you?

That's right - I'm not sure this was a consensual act, or perhaps accepting this male was the female's last earthly act.  Either way, this is the first incidence of insect necrophilia that I have ever witnessed.  I suppose that wont do much for the male's reproductive success - especially if this is indicative of his mate preferences in the future.

Death By Maggot

This leaf-footed bug (family Coreidae) has succumbed to a attack by a parasitic fly.  A fly in the family Tachinidae laid an egg on the bug's head (it is visible near the eye).  The larval fly tunneled out of the bottom of the egg and into the body of its host, where it consumed it from the inside out.  Finally, the maggot chewed out of the coreid and formed the puparium pictured, where it will undergo metamorphosis and emerge as an adult fly.  Tachinid flies are 'parasitoids' because they are parasites that eventually kill their host.

Mantisfly!

I've noticed a few mantispids showing up on some of my favorite blogs in recent weeks, so I thought I'd add my own photos to the trend.  My coworker found this one a few weeks ago.  So far I've only ever seen three of these.  What a cool insect!

 

Garden Food Webs: Lovely Lacewings

 

The flower flies, and ladybugs are not the only predators in my garden.  I occasionally see these green lacewings flying rather clumsily amongst the foliage and flowers.  Their eggs are rather remarkable:

 
 
Ants would carry the eggs away, but all they find is a thin stalk that they cannot climb.  The eggs hatch into hungry larvae - I call them 'alligators.'

 

Green lacewings comprise the insect family Chrysopidae, the Greek root words mean 'golden eye.'  They are rather beautiful and mesmerizing up close:

 

Food webs in the garden: feasting flower flies

Syrphid fly and spiderwort

Most people are familiar with flower flies (also called hover flies), and even those who aren't have probably come across one of the 6000 species in the family Syrphidae.  Recognizing flower flies can be difficult, as many species mimic the yellow and black color patterns of bees and wasps.  Despite their warning colors, the pollen feeding adult flies are harmless.  The offspring of some species, however, are fearsome predators.  The are the stuff of nightmares, if aphids would have bad dreams:

This is what I think it would be like to be eaten by 'The Blob'

These maggots might be confused with caterpillars, as they crawl around on leaf surfaces looking for a meal.  Some species will slime their way through a group of aphids, turning around to consume the now stuck insects at a leisurely pace.  In combination with the ladybird beetles, these have really started to lower the populations of aphids on some of our plants.  Had I not planted a diverse garden that supports other aphids for they syrphids to eat, these predators would not have been around to keep the goldenglow aphids in check.

Not your compost's maggot!

 And for those of you that are feeling terrible about my little red plant-sucking friends, I want to ease your worries: I have reason to believe that aphids do not suffer from night terrors.

Food webs in the garden: ladybug beetles

Name that state insect?

The goldenglow aphids in our garden are under attack!  One of the predators that are most easily spotted are these seven-spot ladybird beetles Cocinella septempunctata.  These familiar insects are attracted not by the aphids themselves, but by chemicals that the plants release only when aphids have been feeding on them.  Both the adult and larval beetles are very efficient aphid predators, plucking them off the plant and chewing up their soft bodies with strong jaws.

Probably Coccinella septempunctata eggs

 Adult beetles lay clusters of eggs on leaves that look like clumps of yellow rice.  If you've ever been bitten by a ladybug larva, you know their jaws can deliver a strong pinch!

nom nom nom

 Cocinella septempunctata is not native to the Americas, but was introduced from Europe and by 1973 was established as part of a biological control program for pest aphid species.  This familiar insect was selected as the state insect of 6 states, including Delaware (I probably would have selected an insect more indicative of the region).  Another introduced coccinellid that I commonly find in our garden is the striking twice-stabbed ladybird beetle Chilocorus kuwanae.  There are native Chilocerus that look very similar but I have not yet seen one here.

Next up: fearsome flower flies!

Food webs in the garden

 Our Oxe-eye Sunflower Heliopsis helianthoides is about to bloom

Over the past several years Kiri and I have been furnishing our garden with plants native to Delaware.  We do this not only because we like these plants, but also to support local wildlife (especially insects of course).  While some pest insects can eat just about anything, most of our desirable insects can only feed on indigenous plant lineages that they co-evolved with.

As our summer flowers are gearing up for a brilliant June display, I have been spending more and more time checking  out the critters that have made their home in our yard.

Aphids give live birth

One of the most apparent visitors are these red aphids that are feeding on some plant stems.  Aphids can reproduce with or without sex, and they are viviparous - having live birth.  This helps them to increase in number very quickly, and sometimes an adult aphid can be seen with a whole row of it's clonal offspring feeding right behind it:

Goldenglow aphids Uroleucon rudbeckiae

Despite their sucking the juices out of our plants, these aphids are a welcome visitor, and I don't worry much about them killing my flowers.  Kiri noticed that while the aphids are host specific, feeding only on our Heliopsis, they do not feed on every plant of that species.  The different plants have slightly different genes, and the aphids prefer certain genotypes on which they are the most successful.  On the preferred plants, they have reached very high numbers, but they have also attracted large numbers of insect predators that attack aphids.

A battle is unfolding amongst our wildflowers as these predators go after the huge aphid colonies - I don't think it's going well for the squishy red plant-suckers.  More on that to follow!

Our garden provides wildlife habitat and a place for me to watch predators and prey!