Saturday, May 16, 2015

Sabino Canyon in May

My friend Ned Harris, in the official uniform of the Santa Catalina Volunteer Patrol (memo to self: take a photo!), and I walked the lower canyon on this overcast cool morning that only around noon turned into a balmy windy day. So the insect world was subdued and the herp-world seemed non-existent for most of the trip. But we still found what cannot hide - nests and sedentary creatures and a few that were driven by a purpose stronger than the instinct to hide in a warm spot.

Here is the turreted entrance to a spider burrow. Big enough for a small tarantula, but tarantulas do not invest in such structures. Large wolf spiders of several genera do, and while I've never seen the inhabitant, I have seen Hogna sp. hunting at night in the vicinity of these turrets. Maybe they build them? According to 'Common Spiders of North America' Hogna builds a burrow with a big entrance (>30 mm) with a turret constructed of silk, grass blades, and small twigs. In this case: dry leaves of Canyon Ragweed.

Our special reason for the trip were these paper wasp nests, and we were happy to find that the cool weather not only kept the wasps at home but also made them extremely approachable. So we were able to document some interesting overlap between two local subspecies of the species Polistes major. The wasps on the left nest are all of the dark brown subspecies (?) Polistes major castaneicolor that I have seen for several years in the location (the roofs of restrooms along the tram line). But on the right nest  you see only two dark individuals (lower right) while the otherones are of the  yellow-brown banded subspecies Polistes major. These two nests were under the same roof, only a few feet apart, but there were more nests like this in other locations, even in a Cain Cholla cactus on Rattlesnake Trail.

In mesquite trees near the dam of the creek, we found clumps of  nymphs of the Giant Mesquite Bug Thasus neocalifornicus, Coreidae. Even against the white sky they were recognizable by their antennal disks. From close up, their colors were dazzling, especially in the diffuse light.

 Their colors are warning colors - they have some dorsal glands that release acidic substances when the bugs are threatened. We smelled it.
 Among all the hundreds of mesquite trees in the lower canyon, only a few have Mesquite bug nymphs all over their developing beans. And not only that, Ned told me that over the years always the same trees were hosting these hungry armies. Since the bugs feed mainly on the developing beans, damage to the trees is difficult to quantify.

Chelinidea vittiger, the Cactus Coreid, was guarding a whole clutch of offspring on on a nearly spineless Opuntia at the Bluff Trail. This genus reminds me of art nouveau  jewelry.

The tiny Zelus renardii, Leafhopper Assassin Bug, nymph, a Reduviid, had caught a gnat nearly its own size. Z. renardii seems to be much more common in Sabino Canyon than Zelus tetracanthus, the dominant species in Madera Canyon. I wonder what the reason may be.

In the cool weather, even flies just sit still to have their photo taken. Here are a Therevid (Stiletto Fly), Tachinid, Tabanid, and a Ulidiid (Picture-winged Flies).

A pair of Nephrotoma sp. (Tiger Crane Flies) are making the best of it. Crane Flies best are adapted to cooler, humid climates. In Arizona they are most often found early in spring or close to riparian areas. This may be N. wulpiana or ferruginea, in which case the riparian forest is the typical habitat.  The larvae inhabit earth or leaf mold and feed on decaying plant debris and grass roots.

A mating aggregation of Lycids (Net-winged beetles) Lucaina discoidalis on Cat Claw Acacia. I find these every year on blooming acacia or mesquite trees. Interestingly, one tree may be absolutely covered in beetles, but there's nothing on the next one. Pheromone attraction may cause these aggregations of hundreds of beetles. Lucaina discoidalis can often be found in mixed groups with Lucaina marginata.

Saguaro and the first Agave blossoms are rarely seen against a cloudy sky. I liked the saturation of all colors provided by the diffuse light.

Shooting a cardinal directly against the white gray sky is still a strange idea, but at the cost of  blowing out all the lighter colors it produced a Japanese-woodcut quality that I like well enough.

And any hummingbird competing with bees for flower space is worth shooting in any light.

Ned just sent me this photo of my approach to one of the wasp nests. I am bracing the camera against the wall, about a foot from the nest. The aggressiveness of Polistes is often overrated.

Tuesday, May 12, 2015

Cottonwood Gall Aphids (Pemphigus populitranversus)

Madera creek is gurgling, Canyon Tree Frogs are croaking, dusky capped Flycatchers are adding their soft whistle and the Cottonwood trees at Proctor Road at Madera Canyon are lush with fresh leaves. The scene rinds me of our excursion to a sky island in Sonora Mexico last spring. There I learned about aphids in leaf-stem galls of cottonwoods, so now I'm actively looking for them. Sure enough, there they are.

Many galls that I find on oaks contain only a single eggs/larvae of a wasp or fly. These galls on cottonwood leaf-stems (petiole) contain a big group of petiolegall aphids, and maybe more than one generation.

A forest service web page helps to understand what my photo shows. the following is a mix of quotations and my own interpretation:
Eggs are laid in fall in bark cracks on Aspen and Cottonwoods. In spring,when new, young leaves appear, eggs hatch into nymphs.  The nymphs feed on developing leaf petioles through their tubular, sucking mouthparts. Feeding induces the host plant to produce a swollen growth, called a gall. The gall completely envelops the developing aphid ( should this be plural or does every nymph get her own?).

'The aphids are pale green with a dark thorax, and covered with a waxy substance'. (Actually, the cavity was nearly filled with that stuff, I removed some to make the aphids visible. They have
short, thread-like antennae and lack the terminal abdominal tubules, the characteristic aphid cornicles. Usually excess sugary fluid is expelled through the cornicles: Honey dew. Inside a gall, this seems not possible. So are the aphids producing the waxy substance instead? It seemed attached to/expelled by those cornicles.
Judging by their size of the aphids I found yesterday I'd say they were still nymphs. They will grow into wingless, asexually reproducing females. These will produce a new generation that will stay within the gall until full-grown. Those new females will have wings. During late June and July the galls will split open, and the winged adults will fly to their summer hosts:
 Plants in the cabbage family. They settle underground on the roots of those herbaceous plants. Several asexual female generations may be produced on the summer host, all living in wax covered colonies. At the end of summer, winged adults emerge and fly back to their winter hosts, the Cottonwood trees, where they give birth to small, mouthless males and females that mate, and then the males die. After mating, each female, which is less than 1/25 inch (1 mm) long, lays one egg that is almost as large as she is into the bark of the host tree and now the cycle is ready to start over.

Saturday, May 2, 2015

Parasitism among arthropods

Insects, like all of us, live in a world of limited resources and try to claim their share. If another organism tries to also use the same, already claimed and often processed resource, we call it parasitism. Parasites can be thieves of provisions (klepto-parasites), invade a host's body (endo-parasites) or just suck its heamolymph (ectoparasites) share the meal of a predator (commensals), smuggle their offspring into a nest (brood parasite), hitch a ride to food .... Parasite host interactions are always interesting and full of complex strategies and behaviors because of course the host tries to prevent the parasite from reaching its goal. But in several cases, surprising symbiotic relationships have evolved over time. As usual, I tackle the topic in its broadest possible form. 

It seems that wherever there are insect eggs or larvae, there are also parasitic wasps around. Here a Platygastrid inspects the eggs of Chelinidea, a cactus bug.

The ichneumon Rhyssa persuasoria is able to find wood boring larvae under inches of wood and determine if they are suited as hosts. She then pushes her incredibly long, thin ovipositor through the wood to place her egg in the wood borer. Some ichneumonids pupate within the host, so the pupa appears draped in the skin of the larva that the wasp larva parasitized.

When I was trying to raise a big caterpillars in Germany as a kid, hundreds of parasitic wasp larvae emerged from it and pupated on the outside of the dying caterpillar. I was so shocked that I did not try raising any butterflies from caterpillars for a very long time. Nowadays, having worked with Dave Wagner, I know a save way to get healthy caterpillars: catch a pregnant female, wait for her to oviposit and raise clean caterpillars from those eggs. Of course, that does not help if you need to solve the mystery of an unidentified caterpillar found in the wild.

 I collected fat green caterpillars from my winter lettuce here in Arizona, and trying to raise them, I invested a lot of extra lettuce leaves, but got only tachinid flies for my efforts. One or rarely two flies hatched per caterpillar and they emerged only after the lepidoptera pupa was formed. The typical barrel shaped fly pupa was found next to the lep pupa which had a big hole at one end.

Tachinid eggs can often be seen firmly attached to adult beetles. The development of the fly has to be quite fast to be completed within the lifespan of this relatively short-lived host.

The big scoliid Campsomeris ephippium seems to be a recent arrival from Mexico. We have been seeing them only since  about 2012 in SE AZ. Their hosts are the grubs of our big scarab beetles like Dynastes. Likely scenario: wasp locates a grub, digs down to it, stabs it to paralyze it, and lays an egg on it: Idiobiont parasitoids.

Many wasps provide paralyzed hosts for their off-spring, the most well known is probably the Tarantula Hawk. But many species in several different families of wasps follow the same pattern, all very host-specific and often with extreme athleticism and surprising orientation capacities. They dig their nests, then go out to find prey, bring it back, lay their egg and close the nest entrance, patting the sand back into place with a rock held between their mandibles.

But even these parasitic wasps have to worry about super-parasites themselves: 
while Ammophila is stashing her big caterpillar into the prepared hole, a little cuckoo is watching. When Ammophila drops her guard for a second, the little Argochrysis wasp slips in and lays her own egg. The egg of the small cuckoo wasp hatches first and probably eats the ammophila egg as well as the caterpillar.

Brood parasitism is extremely common in hymenoptera that provide for their offspring but do not stay around to guard the eggs and larvae. Solitary bee nests produce any number of Bee Flies, Blister Beetles, Wedge-shaped Beetles and Velvet Ants. But may parasites or cuckoos are actually closely related cousins in the same family of bees, for example Megachilidae.

But even ants, who care for their offspring in the most devoted altruistic way have uninvited guests: Several beetle families like weevils, carabids, Bess Beetles and scarabs have members that are adapted to living with ants as nest parasites. They somehow get around the ants' vigilant guards and then feed on the ants' food stores or even their brood.
This anteater scarab, Cremastocheilus mexicanus was flying around some ant hills on Kitt Peak road. In typical fashion, it crash landed and played dead, with legs sticking up ... Now the ants should have come out, ca...rried her into the colony like prey... but once in there, the beetle somehow avoids getting eaten by the ants. I have noticed that she can fold all extremities and even her head very tightly against her body, with no attack point for the ants sticking out. My theory is that this protects her initially against what the ants usually do to beetles: they tear them apart, pulling from all sides. After some time in the ant nest, the beetle might have absorbed enough of the nest-perfume to blend in and for the ants to ignore her, at which point she lays eggs that produce larvae that feed on the rich food supplies and also on the brood of the ants.

There may be more parasitic wasp species than any other group of  parasites, but wasps are also  hosts for a very interesting order of obligatory parasites the Strepsiptera (Twisted-winged Insects):  As I understand it, Taxonomists were not quite sure where the order of Strepsiptera would fit into the phylogenetic tree, but the current understanding is that they are closest to coleoptera (beetles). Their bodies seem highly modified for their lifestyle as endoparasites. At least larvae and females live for the most part of their lives inside the bodies of other arthropods, often in hymenoptera. The short lived winged males fly and find females to mate top left photo). The eggs hatch within the female, who never left  the host, and the young larvae move out from her body cavity to find new hosts.

Many arachnids are exoparasites,  like ticks and many mites. Those often switch from  parasitism as larvae to a predatory life style when mature.  Even those darned chiggers fall into this category. In the picture a  Cobweb spider Euryopis sp. carries a trombidioid larva while a trombidioid adult mite is striking out on its own.

Mites on a carrion beetle are NOT parasitic as in feeding on the beetle or even stealing his food when he carries them to a delectable little corpse. This is an example of phoresy (one animal attached to another exclusively for transport). But the story is interesting, if disgusting to some: The beetle and his mate will bury the dead bird or mouse and masticate it into a ball of food for their larvae. They'll actually stay with their brood and care for them. But before the beetles got a hold of that prize, other insects have already laid eggs on it, for example flies. Supposedly, those phoretic mites,  deutonymphs in the genus Poecilochirus, will destroy that competition, feeding on eggs and small larvae of flies. But being predators, the mites are also a threat to the beetles' own offspring, maybe that's why the beetle parents keep such close watch?
Similar mutualism exists between mites and dung beetles.

Here are more phoretic hitchhikers:  Peudoscorpions, being flightless arachnids and very small, use big strong flighing beetles as public transportation.  Trichocnemis spiculatus neomexicanus is over 2 in long and the pseudoscorpions were hidden under its elytra. But I have also found them clinging to feet and even antennae of beetles, and that probably slows smaller longhorns down considerably.

Avery special case of cohabitation and phoresis was just posted by Alex Wild on Face Book: Attaphila, a tiny cockroach living in Atta (Leafcutter Ant) nests and travelling with young alate queens to their new colonies. See the link here

When predators cannot enjoy their meal in peace, but are joined by flies that are drawn to the smell of the slaughter we call that comensalism - those flies are co-eaters. Here an Assassin Bug (Pselliopus sp.) killed a Mason Wasp (Eumenidae) and a number of  Milichiid flies invited themselves to the feast.

These are only a few examples of the many types of parasitism that can be observed in the insect (or spider world). It is a very complicated and fascinating field.

Saturday, April 11, 2015

Arthropods as builders

Construction projects of the arthropod world: They may be shelters, nurseries, traps for prey, or 'greenhouses' for farming, storage facilities, even floating devices - Arthropods can produce the most amazingly complex and functional structures. To complete those, they may work alone or together with hive members, building with hard labor or by chemically stimulating a host organism to do the work. Structures may be built for duration or destroyed and rebuilt every 24 hours. They may be built for a special event in a life cycle of the insect or for everyday needs.

Many ants build nest mounds. In Germany I often saw huge piles of material containing chambers that contained different stages of larval and pupal development - nurseries that would be moved around within by workers when the temperature changed (Rote Waldameise (Formica rufa)). In other species, piles of soil seem to be just material that is moved out from underground chambers, or refuse that is piled around the entrance of a nest. But the structures that our local leafcutter ant Acromyrmex versicolor builds seem much too well designed to be just piles of refuse. They are perfectly round cones with a crater-like opening when they are new. They erode later, but are often restored. Most colonies have several of these structures. These ants are fungus growers. Their activity level varies very much with season and weather. I assume that they have ways to regulate the growth rate of their fungus gardens in correlation to their own activity level, and I believe that those cones are actually chimneys that control the ventilation of those underground gardens. Either they need more ventilation during high growing seasons, or the ants can even promote faster growth by building higher (or more) chimneys.

 Termites in Africa and Australia build long lasting tall structures, but our Desert Encrusters only work on their adobe structures when the weather is just right after the monsoon rains. They completely cloak dead wood with a layer of mud under which they are protected from the sun while they are slowly rasping away the top layer of dead plant material. Even scar tissue on saguaros gets this treatment. Living tissues are not harmed. Their relatives, the feared subterranean termites, are constructing tell-tale mud tubes to get safely to their deconstruction sites - a thing to be aware of. Some of our termites also build mud turrets as launching platforms for their alates. Every summer, those winged, sexual specimens are waiting within the colony, ready to swarm under just the right weather conditions. When those are perfect, the workers literally push the alates out of those turrets to take flight.

Other mud tubes are the nests of Organ Pipe Mud Daubers. These sphecid Wasps  catch and paralyze spiders as provision for eggs that are placed in rows of chambers covered in mud. These are from Sonora Mexico and were located in a protected spot under an overhanging rock formation.  

Anthidiellum sp., Resin bee, nests, Megachilidae
 Flowers need to seduce insects to visit and pollinate, and the reward is not always nectar. Some flowers offer building materials to their pollinators, for example resin to some species in the family Megachilidae. Female Resin Bees attach single cell nurseries to twigs, some even work little pebbles into the structure.    

Wasps and Hornets developed paper long before even the Chinese knew about it. Chewing cellulose and lignin rich plant material, the insects produce an extremely light and durable building material. Series of hexagonal cells can be tightly packed, forming  structurally sound and expandable mass nurseries and storage chambers. In many cases a thin stylus supports hundreds of cells. The wax honey combs of bees are much heavier, so their builders usually fit them into preexisting niches and cavities.  

 Here in AZ a little Eurasian weevil Coniatus spendidulus is taking on the rapidly spreading tamarisk bush, also from Eurasia. It is not clear whether it was released on purpose or not and it seems to be far less destructive to this botanical pest than some leaf beetles that were introduced. But the tiny guys are interesting in that they have larvae and pupae on the plant surface and do not go into the ground to metamorphose. Instead the last instar larva builds this cage-like cocoon and pupates inside. The whole fragile thing is barely 2 mm long, so I do not know how it protects the pupa, except from falling off the twig.

Leaf-rolling Weevils (family Attelabidae) lay their eggs on oak or Hazel, Alder etc. leaves. The female then cuts the leaf and rolls it very tightly, preserving the mid-rib. The larva lives and develops in the 'nidus' that is formed. But when I collected some, a different, related weevil, the Thief Weevil, hatched. This beetle crawl carefully into the fresh nidus and replace the original egg with her own. So the brown weevil Himatolabus pubescens is the constructor and the blue one, Pterocolus ovatus. is the thief. Did I mention that the thief is a cousin in the same family Attelabidae?
Madera Canyon, April when the oak leaves are fresh

 Many caterpillars use their silk glands to spin protective tubes or pull leaves together as a shelter. But the communal nests of some Tent Caterpillars (Malacosoma) stand out for their in size and strength. In the image you see that the caterpillars enlarged  the nest repeatedly as they grew from tiny hatchlings to 2 in caterpillars. They spend nights and periods of cold weather inside. The metabolism of the caterpillars and their accumulated droppings produce heat. The toughness of the silk walls and shed urticating hairs keep many predators out. But some warblers learn to pick up any caterpillars that venture to the outside. And they need to come out to feed. When they do so, they leave silk strands along their path to guide them back to safety later. Scouts seem to lead the way. The caterpillars can defoliate young wild cherry trees, aspen or willows, but usually the trees will not be harmed permanently. I have collected tent caterpillars for a project and 80% yielded parasitic tachinid flies instead of moths.

:The tiger moth Euchaetes elegans lays her eggs on host milkweeds and covers them with the bright white scales from her belly. I presume this helps protect them from parasites, predation and perhaps the weather, but does nothing to hide them. The mature larva also incorporates hairs into its cocoon. The larva, however, is covered in black, orange and a few white hairs so the cocoon looks nothing like the egg mass. Here in Tucson you can find all stages of this insect during the monsoons, when climbing milkweeds are abundant. Images and text contributed by Randy Hardy

We have moths but also beetles that are called 'case bearer' because their larvae build little covers that they carry around. Our Warty Leaf Beetles look like caterpillar droppings as adults, but their larvae carry these little magician hats. The material is probably feces as in the protective shields of many leaf beetle larvae, plus plant fibers it seems.

Snailcase Bagworm (Apterona helicoidella) and Oiketicus sp.
 Psychidae (Bagworm Moths) Larvae (bagworms) construct snailcase or spindle-shaped bags covered with pieces of twigs, leaves, etc., and remain in them enlarging the bags as they grow -- until they pupate (also in the bag). Adult females remain in the bag even then, emitting pheromones which attract adult males to mate with them. The wingless female then lays her eggs in the protection of the bag.

Plant gall inducers:
Insects of several different orders like hymenoptera and diptera and hemiptera have developed the ability to induce host plants to generate extra tissues especially for their use: plant galls. Unlike tumors, they grow into a very specific shape in a specific place. On the same oak you can find stem and leaf galls, round ones that are smooth and woody and others patterned like marbles or fuzzy like little animals. Most contain a developing insect but some, like the stem galls on Cottonwood, contain a whole colony of aphids.

My friend Jim Zimmermann devoted decades of his retirement to the collection of oak galls in Arizona. He cataloged the host plant and the insects that hatched - often not just the insect that induced the gall to grow (mostly wasps), but also parasites that also used the gall tissue and others that used the  larva of the gall wasp as their host. Secondary parasites of those made the system even more complex. He donated the whole incredible collection to the U of A insect collection and still spends many hours every week working on it and other hymenoptera groups.

Froth produced by a spittlebug nymph, lower right.
Not a yet a permanent,  hard construction (but some relatives of spittlebugs build something similar that calcifies)...
Spittlebug nymphs, like all hemipterans, suck plant juices. Like other plant suckers, they take up much more sap than they need and have to get rid of the excess. While aphids just excrete honey dew and sharp shooters eliminate it in sudden bursts (shots) Spittlebug larvae  produce a blob of foam. It  protects the tender larva from dehydration and overheating, and hides it from parasites and predators.
I always assumed that the froth is very distasteful, wikipedia says acrid ... until one day I noticed that on certain Seepwillows (Baccharis salcilifolia) every blob of spittle had a guest: Paper wasps, flies, and even a teneb beetle were peacefully licking up fluid under the spittle. But they did not attack the nymph inside.

Most of the constructions mentioned so far have been shelters, but some of the  most amazing achievements of all seem to me the webs of spiders. Structures that often combine the functions of shelter and trap. From trip lines to funnel shapes, to wheel like webs with regular spokes, to huge communal hammocks - many different types of web can be produced. The material is released by spinnerets under the spiders's abdomen. The strands can be made for strength or stickiness or even extra light, to allow the spider to float through the air with it. Pictured is the web of a Cribellate Orb Weavers genus Uloborus. The cribellate threads are electro-static, but not sticky.

Build in sand:
Certain antlion larvae dig pits in loose sand to use as traps to catch their prey. They sit buried to their mandibles at the bottom. When ants walk across the pit they lose traction and slide down into the center where the hunter awaits them. If an ant seems likely to escape, the lion tosses sand at it to cause an avalanche that will bring it down.

Construction was a topic that Robyn Waayers proposed as the weekly theme for our insect group on FB. I was going to simply collect my contributions here, but then it just kept growing .... I still have many more ideas, but this blog is too long already

Monday, March 30, 2015

Parental Care among Arthropods

You may think that insects are not really good at it while many arachnids are better. But, as long as the offspring survives it’s probably just exactly the amount of care that’s necessary. In many cases the short-lived parental generation is not around to see the eggs hatch anyway. So the care may all be in the careful placement of the eggs on exactly the right food plant or in the protective microclimate of a nest or at the best spot to hitch a ride with the best foster parents …. Or the care may involve tackling a scary giant as a host or a smelly pile of dung rolled into appetizing portions … 

Canthon imitator, Rio Rico, Santa Cruz Co, AZ
 Some dung beetles are 'tumble bugs'. Using their shovel-shaped heads a pair cuts a round ball out of a fresh pile of dung. Then they roll their prize a considerable distance from its origin, bury it, and the female lays eggs inside it. In some species, the parents stay around to protect and feed the offspring while the larvae grow in their dung ball. Why don't the beetles just drop eggs into the fresh dung and leave? Some flies do it that way? That's just it: dung of big vertebrates still contains many nutrients in a very accessible form, so the competition is great. Beetles, flies, worms, all claim their share. Large dung beetles develop more slowly than many smaller competitors. Also, dung attracts predators. So these parents grab there share and then set up house as far away from the source as possible.

Oncideres rhodosticta (Mesquite Girdler)
 Many wood-boring insects have to deal with the trees self-defense mechanisms. If the larvae are feeding in living parts of the tree they are likely to be gummed up by an avalanche of sticky tree sap. That is the reason why bark beetles are so dangerous during droughts: the tree does not have enough sap to spare to fight back.
In Arizona, we have several longhorn beetles whose larvae grow up in twigs. They are rather host specific, so one uses oaks, another species specializes on mesquite and close relatives.  To guarantee the safety of the larvae, the female chews a grove around the twig, all the way through the cambium to interrupt sugar and water transporting vessels. Often a big glob of accumulated sap can be seen on the tree-side of the cut. But the apical part of the twig is now wilting and dying and defenseless.  That's where the beetle is placing her eggs and where the larvae will grow up. Several other species of insects that are usually drawn to freshly dead wood also find those dying branches. So if you collect those dead branches in a raising box you will usually find a number of different insects emerging.

Melanophila consputa
Freshly dead wood is at a premium for the larvae of wood-boring beetles. Adults of a number of species can be found at wood cuttings or wind breaks where they mate and deposit their eggs. A special situation are trees killed by forest fires.   Buprestids in the genus Melanophila  have pits on the mesosternum that actually detect fires. The females are so drawn to this wood that they may come too close to the fire and burn off their tarsi (feet) while ovipositing.

Neuroctenus sp. with offspring, Santa Rita Mts.
Many true bugs stay with their brood and take care of them.. I still remember hearing recordings of acoustic communication between stink bug mothers and their offspring at the University of Ljubljana when I visited the physiology department there in 1981. It was a squeaking sound that she seemed to  generate by stridulating her proboscis in its grove. The kids were quite obedient, they dispersed at one signal and clustered under mom at another. My photo shows a bug from a different family, a Flat Bug (Aradidae) with very young nymphs and eggs

Our Uloborus spiders live indoors with us. They are pretty safe from most predators and, I must admit, from my dusting as well. But they multiply! They build starshaped eggsacks that hang in their cribellate webs until they suddenly burst into fluffy cotton balls, releasing dozens of miniature spiders. Mom allows them to live in her web for a while and then they build their own ones close to hers. So eventually I will have to oust them ..

Spiders often guard eggs and hatchlings in their webs. But few wolf spiders have webs to call home and they need to get around to hunt. These ambulant species have a characteristic way of lugging their egg-sack around under their abdomen. When the young hatch they climb on mom's back for a wile. I would love to see the mother catch prey. I assume the kids get to eat then, too.
By the way, wolf spiders have a good reason to be vigilant. Wasp Mantisflies are waiting to get their own eggs into that egg-sac ...

Brood parasites wait for every tasty clutch of eggs and even more so for eggs that come provisioned with food. So many eggs are deposited deep within nests which are hidden and sealed. Here a Leafcutter Bee is choosing the wall paper for her nursery. Her nest is in a pre-existing hole, maybe a hole from which a wood-boring beetle has hatched. She covers the walls with her circular cut-outs and she uses them to separate the tunnel into several cells. Each will hold provisions (pollen) and an egg. Males develop faster, so those eggs are placed closer to the exit than those that will become females. Leaves may provide moisture and insulation, but most importantly they have some antifungal and antiseptic qualities that may protect the pollen and the egg.

Polistes major castaneicolor, Queen with 2 workers
 More sophisticated than most other care systems is that of the social hymenoptera. A queen (or several) starts the nest in spring. After she's raised a few new workers, she's got help and can concentrate on her main role: to lay more eggs. The larvae will be tended by the workers, who are their sisters. These females need not reproduce themselves because they share at least as many genes with these larvae as they would with their own offspring.
In Arizona I have always seen dark brown Polistes major castaneicolor. But in early spring I found some solitary wasps that I could not fit into any of our Polistes species. Now I see one of them on each of the new nests, in this case accompanied by 2 of the 'castanaeicolor' individuals. I'm guessing that those are the first daughters of the young queen and hatched from the two cells in the center that contain no eggs. New cells are added on the periphery, so those are younger. You can see the eggs inside. If only the overwintered queen is banded in yellow and rust, it's no wonder that I thought that ALL P. major castaneicolor are brown.